ABSTRACT
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.
ABSTRACT
Androgen insensitivity syndrome (AIS), an X-linked recessive genetic disorder of sex development, is caused by mutations in the androgen receptor (AR) gene, and is characterized by partial or complete inability of specific tissues to respond to androgens in individuals with the 46,XY karyotype. This study aimed to investigate AR gene mutations and to characterize genotype-phenotype correlations. Ten patients from unrelated families, aged 2-31 years, were recruited in the study. Based on karyotype, altered hormone profile, and clinical manifestations, nine patients were preliminarily diagnosed with complete AIS and one with partial AIS. Genetic analysis of AR gene revealed the existence of 10 different mutations, of which five were novel (c.2112 C>G[p.S704R], c.2290T>A[p.Y764N], c.2626C>T[p.Q876X], c.933dupC[p.K313Qfs*28], and c.1067delC[p.A356Efs*123]); the other five were previously reported (c.1789G>A[p.A597T], c.2566C>T[p.R856C], c.2668G>A[p.V890M], c.2679C>T[p.P893L], and c.1605C>G[p.Y535X]). Regarding the distribution of these mutations, 60.0% were clustered in the ligand-binding domain of AR gene. Exons 1 and 8 of AR gene each accounted for 30.0% (3/10) of all mutations. Most of the truncation mutations were in exon 1 and missense mutations were mainly located in exons 4-8. Our study expands the spectrum of AR gene mutations and confirms the usefulness of AR gene sequencing to support a diagnosis of AIS and to enable prenatal or antenatal screening.