Fabry disease is a heritable lipid disorder caused by the low activity of α-galactosidase A and characterized by the systemic accumulation of globotriaosylceramide (Gb3). Recent studies have reported a structural heterogeneity of Gb3 in Fabry disease, including Gb3 isoforms with different fatty acids and Gb3 analogs with modifications on the sphingosine moiety. However, Gb3 assays are often performed only on the selected Gb3 isoforms. To precisely determine the total Gb3 concentration, here we established two methods for determining both Gb3 isoforms and analogs. One was the deacylation method, involving Gb3 treatment with sphingolipid ceramide N-deacylase, followed by an assay of the deacylated products, globotriaosylsphingosine (lyso-Gb3) and its analogs, by ultra-performance LC coupled to tandem MS (UPLC-MS/MS). The other method was a direct assay established in the present study for 37 Gb3 isoforms and analogs/isoforms by UPLC-MS/MS. Gb3s from the organs of symptomatic animals of a Fabry disease mouse model were mainly Gb3 isoforms and two Gb3 analogs, such as Gb3(+18) containing the lyso-Gb3(+18) moiety and Gb3(−2) containing the lyso-Gb3(−2) moiety. The total concentrations and Gb3 analog distributions determined by the two methods were comparable. Gb3(+18) levels were high in the kidneys (24% of total Gb3) and the liver (13%), and we observed Gb3(−2) in the heart (10%) and the kidneys (5%). These results indicate organ-specific expression of Gb3 analogs, insights that may lead to a deeper understanding of the pathophysiology of Fabry disease.

NAD+ is a central metabolite participating in core metabolic redox reactions. The prokaryotic NAD synthetase enzyme NadE catalyzes the last step of NAD+ biosynthesis, converting nicotinic acid adenine dinucleotide (NaAD) to NAD+. Some members of the NadE family use l-glutamine as a nitrogen donor and are named NadEGln. Previous gene neighborhood analysis has indicated that the bacterial nadE gene is frequently clustered with the gene encoding the regulatory signal transduction protein PII, suggesting a functional relationship between these proteins in response to the nutritional status and the carbon/nitrogen ratio of the bacterial cell. Here, using affinity chromatography, bioinformatics analyses, NAD synthetase activity, and biolayer interferometry assays, we show that PII and NadEGln physically interact in vitro, that this complex relieves NadEGln negative feedback inhibition by NAD+. This mechanism is conserved in distantly related bacteria. Of note, the PII protein allosteric effector and cellular nitrogen level indicator 2-oxoglutarate (2-OG) inhibited the formation of the PII-NadEGln complex within a physiological range. These results indicate an interplay between the levels of ATP, ADP, 2-OG, PII-sensed glutamine, and NAD+, representing a metabolic hub that may balance the levels of core nitrogen and carbon metabolites. Our findings support the notion that PII proteins act as a dissociable regulatory subunit of NadEGln, thereby enabling the control of NAD+ biosynthesis according to the nutritional status of the bacterial cell.

Pathogenic bacteria of the genera Mycobacterium and Corynebacterium cause severe human diseases such as tuberculosis (Mycobacterium tuberculosis) and diphtheria (Corynebacterium diphtheriae). The cells of these species are surrounded by protective cell walls rich in long-chain mycolic acids. These fatty acids are conjugated to the disaccharide trehalose on the cytoplasmic side of the bacterial cell membrane. They are then transported across the membrane to the periplasm where they act as donors for other reactions. We have previously shown that transient acetylation of the glycolipid trehalose monohydroxycorynomycolate (hTMCM) enables its efficient transport to the periplasm in Corynebacterium glutamicum and that acetylation is mediated by the membrane protein TmaT. Here, we show that a putative methyltransferase, encoded at the same genetic locus as TmaT, is also required for optimal hTMCM transport. Deletion of the C. glutamicum gene NCgl2764 (Rv0224c in M. tuberculosis) abolished acetyltrehalose monocorynomycolate (AcTMCM) synthesis, leading to accumulation of hTMCM in the inner membrane and delaying its conversion to trehalose dihydroxycorynomycolate (h2TDCM). Complementation with NCgl2764 normalized turnover of hTMCM to h2TDCM. In contrast, complementation with NCgl2764 derivatives mutated at residues essential for methyltransferase activity failed to rectify the defect, suggesting that NCgl2764/Rv0224c encodes a methyltransferase, designated here as MtrP. Comprehensive analyses of the individual mtrP and tmaT mutants and of a double mutant revealed strikingly similar changes across several lipid classes compared with WT bacteria. These findings indicate that both MtrP and TmaT have nonredundant roles in regulating AcTMCM synthesis, revealing additional complexity in the regulation of trehalose mycolate transport in the Corynebacterineae.

Coenzyme Q (Qn) is a vital lipid component of the electron transport chain that functions in cellular energy metabolism and as a membrane antioxidant. In the yeast Saccharomyces cerevisiae, coq1–coq9 deletion mutants are respiratory-incompetent, sensitive to lipid peroxidation stress, and unable to synthesize Q6. The yeast coq10 deletion mutant is also respiratory-deficient and sensitive to lipid peroxidation, yet it continues to produce Q6 at an impaired rate. Thus, Coq10 is required for the function of Q6 in respiration and as an antioxidant and is believed to chaperone Q6 from its site of synthesis to the respiratory complexes. In several fungi, Coq10 is encoded as a fusion polypeptide with Coq11, a recently identified protein of unknown function required for efficient Q6 biosynthesis. Because “fused” proteins are often involved in similar biochemical pathways, here we examined the putative functional relationship between Coq10 and Coq11 in yeast. We used plate growth and Seahorse assays and LC-MS/MS analysis to show that COQ11 deletion rescues respiratory deficiency, sensitivity to lipid peroxidation, and decreased Q6 biosynthesis of the coq10Δ mutant. Additionally, immunoblotting indicated that yeast coq11Δ mutants accumulate increased amounts of certain Coq polypeptides and display a stabilized CoQ synthome. These effects suggest that Coq11 modulates Q6 biosynthesis and that its absence increases mitochondrial Q6 content in the coq10Δcoq11Δ double mutant. This augmented mitochondrial Q6 content counteracts the respiratory deficiency and lipid peroxidation sensitivity phenotypes of the coq10Δ mutant. This study further clarifies the intricate connection between Q6 biosynthesis, trafficking, and function in mitochondrial metabolism.

Kindlins are focal adhesion proteins that regulate integrin activation and outside-in signaling. The kindlin family consists of three members, kindlin-1, -2, and -3. Kindlin-2 is widely expressed in multiple cell types, except those from the hematopoietic lineage. A previous study has reported that the Drosophila Fit1 protein (an ortholog of kindlin-2) prevents abnormal spindle assembly; however, the mechanism remains unknown. Here, we show that kindlin-2 maintains spindle integrity in mitotic human cells. The human neuroblastoma SH-SY5Y cell line expresses only kindlin-2, and we found that when SH-SY5Y cells are depleted of kindlin-2, they exhibit pronounced spindle abnormalities and delayed mitosis. Of note, acetylation of α-tubulin, which maintains microtubule flexibility and stability, was diminished in the kindlin-2–depleted cells. Mechanistically, we found that kindlin-2 maintains α-tubulin acetylation by inhibiting the microtubule-associated deacetylase histone deacetylase 6 (HDAC6) via a signaling pathway involving AKT Ser/Thr kinase (AKT)/glycogen synthase kinase 3β (GSK3β) or paxillin. We also provide evidence that prolonged hypoxia down-regulates kindlin-2 expression, leading to spindle abnormalities not only in the SH-SY5Y cell line, but also cell lines derived from colon and breast tissues. The findings of our study highlight that kindlin-2 regulates mitotic spindle assembly and that this process is perturbed in cancer cells in a hypoxic environment.

(Carnegie Mellon University) Intelligent tutoring systems have been shown to be effective in helping to teach certain subjects, such as algebra or grammar, but creating these computerized systems is difficult and laborious. Now, researchers at Carnegie Mellon University have shown they can rapidly build them by, in effect, teaching the computer to teach.

(University of Massachusetts Lowell) UMass Medical School and UMass Lowell will perform a key role in a new National Institutes of Health initiative aimed at speeding innovation, development and commercialization of COVID-19 testing technologies via their Center for Advancing Point of Care Technologies collaboration.

(Michigan Medicine - University of Michigan) They know it's addictive. They know it's linked to dangerous lung diseases. And they know it delivers more nicotine than the cigarettes it's supposed to replace. But the social aspects of vaping drives young people to use Juul and other e-cigarettes, according to nearly two-thirds of teens and young adults in a new study. Less than 5% say the availability of fruity flavors drives use of e-cigarettes by members of their generation, and only 10% say addiction does.

Residents may have seen a distinctive white car, fitted with advanced imaging and sensory gadgetry, on its journey to create the next generation of Hong Kong maps.

As it travels up and down the city’s streets, it records the three-dimensional shapes of buildings ranging from the iconic Convention & Exhibition Centre to the Customs Headquarters Building, and even primary school campuses.

The vehicle, dubbed the Mobile Mapping System, is one of the latest technologies used by the Lands Department to survey the city.

Five pieces of equipment work in concert to collect detailed information for the 3D City Map - a core component of the digital infrastructure underpinning Hong Kong’s smart city development.

A high-resolution camera on top of the vehicle captures 360-degree images and a 3D laser scanner collects spatial measurements. An inertial navigation system and a global navigation satellite system receiver provide precise positioning.

Lands Department Assistant Land Surveyor Charlie Hung said one of the biggest advantages of this system is its ability to quickly and efficiently acquire data, which can be used to enrich 3D models and enhance existing maps.

“We can enhance the attributed information of our basic map. For example, the lamppost number, the building name or the street number.”

Drones are also used to map the city, she added. However, air surveying may not be suitable for collecting data from ground level. This is where the Mobile Mapping System vehicle comes into play.

Better data

The 3D City Map is part of the 3D Digital Map Development, which aims to contribute to an innovative, sustainable and smart Hong Kong.

Compared with traditional maps, the 3D City Map can provide more accurate and abundantly better spatial data.

The map will cover the entire city by 2023, serving as a handy tool for analysis and planning, according to Lands Department Land Surveyor Ben Fan.

He said: “Based on the 3D digital map, we can develop various kinds of applications such as land administration, environmental assessment, town planning and also transport and engineering studies.”

The latest transport infrastructures such as the Hong Kong-Zhuhai-Macao Bridge, the Central-Wan Chai Bypass and the Heung Yuen Wai Highway have also been scanned.

In the next stage of the 3D Digital Map Development, the department will create the 3D Indoor Map. As a start, data from 150 buildings in Kowloon East will be collected first before extending to other buildings in the city.

The last stage 3D models of objects such as trees and lampposts for city modelling will be produced.

(American Association for Cancer Research) Combining intratumoral electroporation of interleukin-12 (IL-12) DNA (tavokinogene telseplasmid, or TAVO) with the immune checkpoint inhibitor pembrolizumab (Keytruda) led to clinical responses in patients with immunologically quiescent advanced melanoma, according to results from a phase II trial.

(JAMA Network) Death certificate data were used to compare the rate of opioid-related deaths in the US among cancer survivors with that of the general population from 2006 through 2016. Whether opioid-associated deaths in cancer survivors, who are often prescribed opioids for cancer-related pain, are rising at the same rate as in the general population is unknown.

(University of Houston) A University of Houston biomedical researcher is developing a new device to treat babies with blood disorders, because current technology is designed for adults. The ability to perform lifesaving leukapheresis safely and effectively in these most vulnerable pediatric patients will significantly increase their access to highly effective cell-based therapies.

(George Mason University) The team's work supports evidence-based decision making, informed by models, to rethink and facilitate hospital operations during the pandemic.

(Michigan Medicine - University of Michigan) Now, as hospitals across the country start to return to doing non-emergency operations that keep their beds full and their books balanced, they need to think carefully about what resources each of those procedures will need as the pandemic continues. A new guide could help them prioritize and plan. Created by poring over seven years' worth of data from 17 common operations in dozens of hospitals, it's available for free for any hospital to use.

(Simon Fraser University) SFU professor Caroline Colijn’s research and data modelling to map the spread of COVID-19 in British Columbia has helped her procure funding from Genome B.C., a non-profit research organization that leads genomics innovation on Canada’s West Coast.

(University of Massachusetts Lowell) A UMass Lowell researcher investigating how to identify damage in wind turbines before they fail has received $1.4 million to develop a solution.

(International Astronomical Union) The Gruber Cosmology Prize, which is co-sponsored by the IAU, recognises scientists whose discoveries have driven fundamental advances in our understanding of the Universe. The 2020 prize has been awarded to Lars Hernquist and Volker Springel for their pioneering work on cosmological simulations, which have not only led to their own discoveries, but also become an invaluable resource used widely by other researchers.

(University of Michigan) The coronavirus pandemic has highlighted just how reliant the United States and other countries are on Chinese manufacturing, with widespread shortages of protective medical gear produced there.

(Smithsonian Tropical Research Institute) Oil pollution is known to cause lethal and sublethal responses on coral communities in the short-term, but its long-term effects have not been widely studied. The Bahia Las Minas oil spill, which contaminated about 40 square kilometers (about 15 square miles) near the Smithsonian's Galeta Point Marine Laboratory in Colon and became the largest recorded near coastal habitats in Panama, served as an opportunity to understand how coral reefs in tropical ecosystems recover from acute contamination over time.

(NOAA Headquarters) While the global average number of tropical cyclones each year has not budged from 86 over the last four decades, climate change has been influencing the locations of where these deadly storms occur, according to new NOAA-led research published in Proceedings of the National Academy of Science.

The streets of Chicago may be largely empty as residents hunker down from coronavirus but some of the city's most deprived neighborhoods are still echoing to the sound of deadly gunfire and raucous partying. While significant falls in crime have been one of the few positive side effects of lockdowns in much of the United States and elsewhere, they have barely made a dent in the homicide rate in Chicago, a city that has long recorded the most murders in the country. Chicago police say 56 murders were committed in April despite statewide stay-at-home orders -- only a fraction lower than the 61 for the same month in 2019 -- while last weekend, the first of the new month, four people were killed and 46 others shot and wounded.

Russia's GRU military intelligence service appears to have got hold of many emails from Chancellor Angela Merkel's constituency office in a 2015 hack attack on Germany's parliament, Der Spiegel magazine reported on Friday, without citing its sources. A spokesman for the German government had no immediate comment. Der Spiegel said federal criminal police and the federal cyber agency had been able to partially reconstruct the attack and found that two email inboxes from Merkel's office had been targeted.

A coronavirus test – which aims to deliver rapid results – has received major funding.

Imperial's disease outbreak centre J-IDEA has launched a pandemic hospital planning tool to help cope with extreme surges in demand from coronavirus.

(Osaka University) Researchers from Osaka University and Mandom Corporation succeeded in generating immortalized myoepithelial cells in human eccrine sweat glands, providing a novel test system for research on human sweating.

(American Geriatrics Society) The American Geriatrics Society (AGS) today announced that John B. Murphy, MD, a clinician, educator, and administrator working to embed geriatrics education in the fabric of medical curricula and clinical operations will be honored with the 2020 Dennis W. Jahnigen Award celebrating work to train health professionals in the care we all need as we age.

(University of Surrey) A new research study, investigating how service robots in hotels could help redefine leadership and boost the hospitality industry, has taken on new significance in the light of the seismic impact of the Covid-19 outbreak on tourism and business travel. The study by academics at The University of Surrey and MODUL University Vienna focuses on how HR experts perceive service robots and their impact on leadership and HR management in the hotel industry.

Carlos E. Mendez
Aug 1, 2014; 27:180-188
From Research to Practice

Cynthia Payne
Aug 1, 2001; 14:
Preface

Karen B. Hirschman
Aug 1, 2014; 27:192-195
From Research to Practice

Martha Mitchell Funnell
Oct 1, 2007; 20:221-226
Articles

Stephen F. Quevedo
Oct 1, 2001; 14:
Feature Articles

Up-and-coming entertainer Shav-A says the COVID-19 pandemic made her reflect on her life. "I needed a reset. With all this downtime, I have realised that I needed to stop and rethink a lot of things that are going on in my life, and it also...

Residents of Love Street, a section of Jones Town in Kington, say the area has been suffering from a chronic water shortage for more than two months. Daniesha Taylor, who has lived in the community for 30 years, is fearful that the lack of water...

Liz Wilkes ’13, CEO of Exubrancy, knows mental and physical well-being is more important now than ever before.

The canonical pathway of eicosanoid production in most mammalian cells is initiated by phospholipase A2-mediated release of arachidonic acid, followed by its enzymatic oxidation resulting in a vast array of eicosanoid products. However, recent work has demonstrated that the major phospholipase in mitochondria, iPLA2γ (patatin-like phospholipase domain containing 8 (PNPLA8)), possesses sn-1 specificity, with polyunsaturated fatty acids at the sn-2 position generating polyunsaturated sn-2-acyl lysophospholipids. Through strategic chemical derivatization, chiral chromatographic separation, and multistage tandem MS, here we first demonstrate that human platelet-type 12-lipoxygenase (12-LOX) can directly catalyze the regioselective and stereospecific oxidation of 2-arachidonoyl-lysophosphatidylcholine (2-AA-LPC) and 2-arachidonoyl-lysophosphatidylethanolamine (2-AA-LPE). Next, we identified these two eicosanoid-lysophospholipids in murine myocardium and in isolated platelets. Moreover, we observed robust increases in 2-AA-LPC, 2-AA-LPE, and their downstream 12-LOX oxidation products, 12(S)-HETE-LPC and 12(S)-HETE-LPE, in calcium ionophore (A23187)-stimulated murine platelets. Mechanistically, genetic ablation of iPLA2γ markedly decreased the calcium-stimulated production of 2-AA-LPC, 2-AA-LPE, and 12-HETE-lysophospholipids in mouse platelets. Importantly, a potent and selective 12-LOX inhibitor, ML355, significantly inhibited the production of 12-HETE-LPC and 12-HETE-LPE in activated platelets. Furthermore, we found that aging is accompanied by significant changes in 12-HETE-LPC in murine serum that were also markedly attenuated by iPLA2γ genetic ablation. Collectively, these results identify previously unknown iPLA2γ-initiated signaling pathways mediated by direct 12-LOX oxidation of 2-AA-LPC and 2-AA-LPE. This oxidation generates previously unrecognized eicosanoid-lysophospholipids that may serve as biomarkers for age-related diseases and could potentially be used as targets in therapeutic interventions.

Fatty acid transport protein 2 (FATP2) is highly expressed in the liver, small intestine, and kidney, where it functions in both the transport of exogenous long-chain fatty acids and the activation of very-long-chain fatty acids. Here, using a murine model, we investigated the phenotypic impacts of deleting FATP2, followed by a transcriptomic analysis using unbiased RNA-Seq to identify concomitant changes in the liver transcriptome. WT and FATP2-null (Fatp2−/−) mice (5 weeks) were maintained on a standard chow diet for 6 weeks. The Fatp2−/− mice had reduced weight gain, lowered serum triglyceride, and increased serum cholesterol levels and attenuated dietary fatty acid absorption. Transcriptomic analysis of the liver revealed 258 differentially expressed genes in male Fatp2−/− mice and a total of 91 in female Fatp2−/− mice. These genes mapped to the following gene ontology categories: fatty acid degradation, peroxisome biogenesis, fatty acid synthesis, and retinol and arachidonic acid metabolism. Targeted RT-quantitative PCR verified the altered expression of selected genes. Of note, most of the genes with increased expression were known to be regulated by peroxisome proliferator–activated receptor α (PPARα), suggesting that FATP2 activity is linked to a PPARα-specific proximal ligand. Targeted metabolomic experiments in the Fatp2−/− liver revealed increases of total C16:0, C16:1, and C18:1 fatty acids; increases in lipoxin A4 and prostaglandin J2; and a decrease in 20-hydroxyeicosatetraenoic acid. We conclude that the expression of FATP2 in the liver broadly affects the metabolic landscape through PPARα, indicating that FATP2 provides an important role in liver lipid metabolism through its transport or activation activities.

Fabry disease is a heritable lipid disorder caused by the low activity of α-galactosidase A and characterized by the systemic accumulation of globotriaosylceramide (Gb3). Recent studies have reported a structural heterogeneity of Gb3 in Fabry disease, including Gb3 isoforms with different fatty acids and Gb3 analogs with modifications on the sphingosine moiety. However, Gb3 assays are often performed only on the selected Gb3 isoforms. To precisely determine the total Gb3 concentration, here we established two methods for determining both Gb3 isoforms and analogs. One was the deacylation method, involving Gb3 treatment with sphingolipid ceramide N-deacylase, followed by an assay of the deacylated products, globotriaosylsphingosine (lyso-Gb3) and its analogs, by ultra-performance LC coupled to tandem MS (UPLC-MS/MS). The other method was a direct assay established in the present study for 37 Gb3 isoforms and analogs/isoforms by UPLC-MS/MS. Gb3s from the organs of symptomatic animals of a Fabry disease mouse model were mainly Gb3 isoforms and two Gb3 analogs, such as Gb3(+18) containing the lyso-Gb3(+18) moiety and Gb3(−2) containing the lyso-Gb3(−2) moiety. The total concentrations and Gb3 analog distributions determined by the two methods were comparable. Gb3(+18) levels were high in the kidneys (24% of total Gb3) and the liver (13%), and we observed Gb3(−2) in the heart (10%) and the kidneys (5%). These results indicate organ-specific expression of Gb3 analogs, insights that may lead to a deeper understanding of the pathophysiology of Fabry disease.

Pathogenic bacteria of the genera Mycobacterium and Corynebacterium cause severe human diseases such as tuberculosis (Mycobacterium tuberculosis) and diphtheria (Corynebacterium diphtheriae). The cells of these species are surrounded by protective cell walls rich in long-chain mycolic acids. These fatty acids are conjugated to the disaccharide trehalose on the cytoplasmic side of the bacterial cell membrane. They are then transported across the membrane to the periplasm where they act as donors for other reactions. We have previously shown that transient acetylation of the glycolipid trehalose monohydroxycorynomycolate (hTMCM) enables its efficient transport to the periplasm in Corynebacterium glutamicum and that acetylation is mediated by the membrane protein TmaT. Here, we show that a putative methyltransferase, encoded at the same genetic locus as TmaT, is also required for optimal hTMCM transport. Deletion of the C. glutamicum gene NCgl2764 (Rv0224c in M. tuberculosis) abolished acetyltrehalose monocorynomycolate (AcTMCM) synthesis, leading to accumulation of hTMCM in the inner membrane and delaying its conversion to trehalose dihydroxycorynomycolate (h2TDCM). Complementation with NCgl2764 normalized turnover of hTMCM to h2TDCM. In contrast, complementation with NCgl2764 derivatives mutated at residues essential for methyltransferase activity failed to rectify the defect, suggesting that NCgl2764/Rv0224c encodes a methyltransferase, designated here as MtrP. Comprehensive analyses of the individual mtrP and tmaT mutants and of a double mutant revealed strikingly similar changes across several lipid classes compared with WT bacteria. These findings indicate that both MtrP and TmaT have nonredundant roles in regulating AcTMCM synthesis, revealing additional complexity in the regulation of trehalose mycolate transport in the Corynebacterineae.

Coenzyme Q (Qn) is a vital lipid component of the electron transport chain that functions in cellular energy metabolism and as a membrane antioxidant. In the yeast Saccharomyces cerevisiae, coq1–coq9 deletion mutants are respiratory-incompetent, sensitive to lipid peroxidation stress, and unable to synthesize Q6. The yeast coq10 deletion mutant is also respiratory-deficient and sensitive to lipid peroxidation, yet it continues to produce Q6 at an impaired rate. Thus, Coq10 is required for the function of Q6 in respiration and as an antioxidant and is believed to chaperone Q6 from its site of synthesis to the respiratory complexes. In several fungi, Coq10 is encoded as a fusion polypeptide with Coq11, a recently identified protein of unknown function required for efficient Q6 biosynthesis. Because “fused” proteins are often involved in similar biochemical pathways, here we examined the putative functional relationship between Coq10 and Coq11 in yeast. We used plate growth and Seahorse assays and LC-MS/MS analysis to show that COQ11 deletion rescues respiratory deficiency, sensitivity to lipid peroxidation, and decreased Q6 biosynthesis of the coq10Δ mutant. Additionally, immunoblotting indicated that yeast coq11Δ mutants accumulate increased amounts of certain Coq polypeptides and display a stabilized CoQ synthome. These effects suggest that Coq11 modulates Q6 biosynthesis and that its absence increases mitochondrial Q6 content in the coq10Δcoq11Δ double mutant. This augmented mitochondrial Q6 content counteracts the respiratory deficiency and lipid peroxidation sensitivity phenotypes of the coq10Δ mutant. This study further clarifies the intricate connection between Q6 biosynthesis, trafficking, and function in mitochondrial metabolism.

Sperm head shaping is a key event in spermiogenesis and is tightly controlled via the acrosome–manchette network. Linker of nucleoskeleton and cytoskeleton (LINC) complexes consist of Sad1 and UNC84 domain–containing (SUN) and Klarsicht/ANC-1/Syne-1 homology (KASH) domain proteins and form conserved nuclear envelope bridges implicated in transducing mechanical forces from the manchette to sculpt sperm nuclei into a hook-like shape. However, the role of LINC complexes in sperm head shaping is still poorly understood. Here we assessed the role of SUN3, a testis-specific LINC component harboring a conserved SUN domain, in spermiogenesis. We show that CRISPR/Cas9-generated Sun3 knockout male mice are infertile, displaying drastically reduced sperm counts and a globozoospermia-like phenotype, including a missing, mislocalized, or fragmented acrosome, as well as multiple defects in sperm flagella. Further examination revealed that the sperm head abnormalities are apparent at step 9 and that the sperm nuclei fail to elongate because of the absence of manchette microtubules and perinuclear rings. These observations indicate that Sun3 deletion likely impairs the ability of the LINC complex to transduce the cytoskeletal force to the nuclear envelope, required for sperm head elongation. We also found that SUN3 interacts with SUN4 in mouse testes and that the level of SUN4 proteins is drastically reduced in Sun3-null mice. Altogether, our results indicate that SUN3 is essential for sperm head shaping and male fertility, providing molecular clues regarding the underlying pathology of the globozoospermia-like phenotype.

Quentin Perraud
Apr 1, 2020; 19:589-607
Research