Identification and Characterization of the Most Common Genetic Variant Responsible for Acephalic Spermatozoa Syndrome in Men Originating from North Africa.
Acephalic spermatozoa syndrome (ASS) is a rare but extremely severe type of teratozoospermia, defined by the presence of a majority of headless flagella and a minority of tail-less sperm heads in the ejaculate. Like the other severe monomorphic teratozoospermias, ASS has a strong genetic basis and is most often caused by bi-allelic variants in SUN5 (Sad1 and UNC84 domain-containing 5). Using whole exome sequencing (WES), we investigated a cohort of nine infertile subjects displaying ASS. These subjects were recruited in three centers located in France and Tunisia, but all originated from North Africa. Sperm from subjects carrying candidate genetic variants were subjected to immunofluorescence analysis and transmission electron microscopy. Moreover, fluorescent in situ hybridization (FISH) was performed on sperm nuclei to assess their chromosomal content. Variant filtering permitted us to identify the same SUN5 homozygous frameshift variant (c.211+1_211+2dup) in 7/9 individuals (78%). SUN5 encodes a protein localized on the posterior part of the nuclear envelope that is necessary for the attachment of the tail to the sperm head. Immunofluorescence assays performed on sperm cells from three mutated subjects revealed a total absence of SUN5, thus demonstrating the deleterious impact of the identified variant on protein expression. Transmission electron microscopy showed a conserved flagellar structure and a slightly decondensed chromatin. FISH did not highlight a higher rate of chromosome aneuploidy in spermatozoa from SUN5 patients compared to controls, indicating that intra-cytoplasmic sperm injection (ICSI) can be proposed for patients carrying the c.211+1_211+2dup variant. These results suggest that the identified SUN5 variant is the main cause of ASS in the North African population. Consequently, a simple and inexpensive genotyping of the 211+1_211+2dup variant could be beneficial for affected men of North African origin before resorting to more exhaustive genetic analyses.
['Cazin|Caroline|C|', 'Boumerdassi|Yasmine|Y|0000-0003-2381-443X', 'Martinez|Guillaume|G|', 'Fourati Ben Mustapha|Selima|S|', 'Whitfield|Marjorie|M|', 'Coutton|Charles|C|', 'Thierry-Mieg|Nicolas|N|', 'Di Pizio|Pierre|P|', 'Rives|Nathalie|N|', 'Arnoult|Christophe|C|', 'Touré|Aminata|A|0000-0001-5629-849X', 'Ray|Pierre F|PF|0000-0003-1544-7449', 'Zouari|Raoudha|R|', 'Sifer|Christophe|C|', 'Kherraf|Zine-Eddine|ZE|']
D000328:Adult D000352:Africa, Northern D000782:Aneuploidy D016022:Case-Control Studies D014644:Genetic Variation D006239:Haplotypes D006720:Homozygote D006801:Humans D017404:In Situ Hybridization, Fluorescence D008297:Male D008565:Membrane Proteins D008875:Middle Aged D013094:Spermatozoa D000072660:Teratozoospermia D000073359:Whole Exome Sequencing
acephalic spermatozoa syndrome teratozoospermia SUN5 whole exome sequencing genetics of male infertility