A novel homozygous frameshift mutation in MNS1 associated with severe oligoasthenoteratozoospermia in humans

Oligoasthenoteratozoospermia(OAT)refers to the combination of various sperm abnormalities,including a decreased sperm count,reduced motility,and abnormal sperm morphology.Only a few genetic causes have been shown to be associated with OAT.Herein,we identified a novel homozygous frameshift mutation in meiosis-specific nuclear structural 1(MNS1;NM_018365:c.603_604insG:p.Lys202Glufs*6)by whole-exome sequencing in an OAT proband from a consanguineous Chinese family.Subsequent variant screening identified four additional heterozygous MNS1 variants in 6/219 infertile individuals with oligoasthenospermia,but no MNS1 variants were observed among 223 fertile controls.Immunostaining analysis showed MNS1 to be normally located in the whole-sperm flagella,but was absent in the proband's sperm.Expression analysis by Western blot also confirmed that MNS1 was absent in the proband's sperm.Abnormal flagellum morphology and ultrastructural disturbances in outer doublet microtubules were observed in the proband's sperm.A total of three intracytoplasmic sperm injection cycles were carried out for the proband's wife,but they all failed to lead to a successful pregnancy.Overall,this is the first study to report a loss-of-function mutation in MNS1 causing OAT in a Han Chinese patient.

Improving native human sperm freezing protection by using a modified vitrification method

Slow freezing is the most commonly used technique for the cryopreservation of spermatozoa in clinical practice.However,it has been shown to have a negative impact on sperm function and structure.Vitrification as a successful alternative method has been proved to have better protective effects on human embryos,but vitrification of spermatozoa is still subject to low recovery rates.In this study,a modified vitrification method for native spermatozoa was developed.A total of 28 semen samples were included;each sample was divided into three equal parts and assigned to fresh,slow freezing,and vitrification groups.Sperm vitality,motility,morphology,DNA integrity,and acrosome reaction were assessed for each of the groups.The results showed that vitrification achieves better results for several sperm protection parameters than slow freezing;vitrification achieves a higher recovery rate(P<0.05),motility(P<0.05),morphology(P<0.05),and curve line velocity(P<0.05)than slow freezing.Furthermore,DNA fragmentation was decreased(P<0.05)and better acrosome protection(P<0.05)was exhibited in the spermatozoa after vitrification.Principal component analysis of all sperm parameters revealed that the vitrification cluster was closer to the fresh cluster,indicating that spermatozoa are better preserved through vitrification.In conclusion,while both slow freezing and vitrification have negative effects on sperm function and structure,the vitrification protocol described here had a relatively better recovery rate(65.8%)and showed improved preservation of several sperm quality parameters compared with slow freezing.