Two novel mutations in PADI6 and TLE6 genes cause female infertility due to arrest in embryonic development

Abstract

Purpose This study aims to identify genetic causes of female infertility associated with recurrent failure of assisted reproductive technology (ART) characterized by embryonic developmental arrest. Methods We recruited infertile patients from two consanguineous families from the Reproductive Medicine Center of Guizhou Provincial People’s Hospital. Peripheral blood was collected for genomic DNA extraction. Two affected individuals and their family members were performed with whole-exome sequencing and Sanger validation in order to identify possible causative genes. For further analyzing the effect of splicing mutation on mRNA integrity in vivo, TLE6 cDNA from the peripheral blood lymphocyte of the affected individual was sequenced. In addition, the possible impact of the pathogenic mutation on the structure and function of the protein were also assessed. Results Two novel homozygous mutations in the peptidylarginine deiminase type VI (PADI6) and the transducin-like enhancer of split 6 (TLE6) genes were identified in the two families. One patient carried the frameshift deletion mutation c.831_832del:p.S278Pfs*59 of the PADI6 gene and the other patient carried the splicing mutation c.1245-2 A>G of the TLE6 gene. The analysis of the mRNA from the proband’s peripheral blood leukocytes confirmed aberrant splicing. Conclusions Our findings expand the mutational spectrum of PADI6 and TLE6 associated with embryonic developmental arrest and deepen our understanding of the genetic causes of infertility with recurrent ART failure.

A novel homozygous mutation in the PADI6 gene causes early embryo arrest

“…In this study, a homozygous mutation c.558dupA (p.T187Nfs*48) caused early embryonic arrest in the proband (II-2), resulting in 3- or 5-cell arrested embryos on Day 3 and no viable blastocytes on Day 5, which was congruent with previous reports [ 8 , 9 , 23 – 25 ]. Due to the limitation of the PADI6 antibody for immunofluorescence, we did not investigate the in vivo expression of PADI6 in the oocytes of the patient.…”

“…The PADI family is comprised of five members, including PADI1 , PADI2 , PADI3 , PADI4 , and PADI6 . Among these, PADI6 is exclusively expressed in oocytes and early embryos [ 9 ]. PADI6 is one of SCMC components that localizes to other components in oocytes and early embryos.…”

“…Early human embryos (before the eight-cell stages) are transcriptionally silent and utilize maternally provided transcripts and proteins during the maturation process of growing oocytes [ 7 ]. Human subcortical maternal complex (SCMC) is a multiprotein complex uniquely located in the subcortex of the mammalian oocytes and embryos, which mainly consists of eight proteins, including TLE6 , NLRP2 , NLRP5 , NLRP7 , oocyte permitting embryonic development ( OOEP ), KHDC3L and PADI6 , and zinc finger BED-type containing 3 ( ZBED3 ) [ 8 , 9 ]. SCMC is an important maternal-effect factor.…”

Genetics of Oocyte Maturation Defects and Early Embryo Development Arrest

“…Pathogenic loss-of-function variants in PADI6 have been also described in the mothers of children with sporadic Beckwith–Wiedemann syndrome with MLID [ 61 ]. Biallelic variants in PADI6 cause female infertility characterized as early embryonic developmental arrest, zygotic cleavage failure, and recurrent hydatidiform moles [ 62 , 63 , 64 , 65 , 66 ]. An in vitro expression study showed a significant decrease in PADI6 in mutation models, which may disturb the stability of the SCMC complex [ 62 ].…”

“…In mouse models, the knockout of the Tle6 gene has no effect on oogenesis but results in embryonic developmental arrest at the 2-cell stage, leading to female mouse infertility [ 48 , 67 ]. Homozygous and compound-heterozygous variants in the TLE6 gene are associated with various phenotypes, including fertilization failure, early cleavage failure, embryonic developmental arrest on day 3, and a high rate of embryo fragmentation due to the disruption of F-actin and spindle assembly [ 14 , 66 , 68 , 69 ]. A woman with a heterozygous variant in TLE6 had normal fertility and two healthy children [ 69 ].…”