Recurrent pregnancy loss (RPL) is a major concern for women's reproductive health. Several studies have proved that genetics is a major factor leading to unexplained RPL, but the maternal pathogenic genes involved in RPL remain largely unknown. A consanguineous family, including the parents who were cousins and their three daughters who had been diagnosed as having nonsyndromic unexplained RPL, was recruited in this study. A rare homozygous variant in calcyphosine (CAPS; ENST00000588776: c.377delC, p.Leu127Trpfs) might be the potential candidate variant for this RPL family through whole-exome sequencing. Sanger sequencing confirmed that the three affected sisters carried the homozygous p.Leu127Trpfs, whereas their parents carried the heterozygous p.Leu127Trpfs. CAPS encodes a Ca2+-binding protein and may play a role in the regulation of Ca2+ transport. Although the precise underlying mechanisms remain unclear, the previous study suggested that they may be involved in cross talk between Ca2+ signaling and cAMP-protein kinase A pathways, which are crucial to embryo implantation and pregnancy maintenance. Knockdown of CAPS expression might promote the expression of secreted phosphoprotein 1 and matrix metalloproteinase 9, and the release of prostaglandin E2, which all played important roles in embryo implantation and early pregnancy maintenance. These results indicated that the autosomal recessive homozygous mutation, p.Leu127Trpfs, in CAPS might be a maternal effect causative mutation of RPL pathogenesis.
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