Arafat Maram, Harlev Avi, Har-Vardi Iris, Levitas Eliahu, Priel Tsvia, Gershoni Moran, Searby Charles, Sheffield Val C, Lunenfeld Eitan, Parvari Ruti
The Shraga Segal Department of Microbiology, Immunology & Genetics, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel.
The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer Sheva, Israel.
J Med Genet. 2020 Jun 5. doi: 10.1136/jmedgenet-2019-106825.
Oligoteratoasthenozoospermia (OTA) combines deteriorated quantity, morphology and motility of the sperm, resulting in male factor infertility.
We used whole genome genotyping and exome sequencing to identify the mutation causing OTA in four men in a consanguineous Bedouin family. We expressed the normal and mutated proteins tagged with c-Myc at the carboxy termini by transfection with pCDNA3.1 plasmid constructs to evaluate the effects on protein stability in HEK293 cells and on the kinetics of actin repolymerisation in retinal pigment epithelium cells. Patients' sperm samples were visualised by transmission electron microscopy to determine axoneme structures and were stained with fluorescent phalloidin to visualise the fibrillar (F)-actin.
A homozygous missense mutation in Ciliogenesis Associated TTC17 Interacting Protein (): c. T103A, p. Phe35Ile, a gene encoding a protein important in actin organisation and ciliogenesis, was identified as the causative mutation with a LOD score of 3.25. The mutation reduces the protein stability compared with the normal protein. Furthermore, overexpression of the normal protein, but not the mutated protein, inhibits repolymerisation of actin after disruption with cytochalasin D. A high percentage of spermatozoa axonemes from patients have abnormalities, as well as disturbances in the distribution of F-actin.
This is the first report of a recessive mutation in in humans. The identified mutation may contribute to asthenozoospermia by its involvement in actin polymerisation and on the actin cytoskeleton. A mouse knockout homozygote for CATIP was reported to demonstrate male infertility as the sole phenotype.
少弱畸精子症（OTA）合并精子数量减少、形态异常和活力下降，导致男性因素不育。
我们利用全基因组基因分型和外显子组测序，在一个近亲结婚的贝都因家族的四名男性中鉴定出导致OTA的突变。我们通过用pCDNA3.1质粒构建体转染，在羧基末端表达标记有c-Myc的正常和突变蛋白，以评估其对HEK293细胞中蛋白质稳定性以及视网膜色素上皮细胞中肌动蛋白再聚合动力学的影响。通过透射电子显微镜观察患者的精子样本以确定轴丝结构，并用荧光鬼笔环肽染色以观察丝状（F）-肌动蛋白。
在纤毛发生相关TTC17相互作用蛋白（）中发现一个纯合错义突变：c.T103A，p.Phe35Ile，该基因编码一种在肌动蛋白组织和纤毛发生中起重要作用的蛋白质，被鉴定为致病突变，LOD评分为3.25。与正常蛋白相比，该突变降低了蛋白质稳定性。此外，正常蛋白而非突变蛋白的过表达抑制了细胞松弛素D破坏后肌动蛋白的再聚合。患者的高比例精子轴丝存在异常，以及F-肌动蛋白分布紊乱。
这是人类中首次关于该基因隐性突变的报道。所鉴定的突变可能通过参与肌动蛋白聚合和肌动蛋白细胞骨架而导致弱精子症。据报道，CATIP基因敲除纯合子小鼠表现出雄性不育作为唯一表型。
