ZP1 and Infertility: Analysis of the nucleotide sequence of ZP1 gene from six members of the family (five sisters and one brother; four sisters diagnosed with primary infertility; two out of four sisters had eggs which were not surrounded with ZP matrix, other two sisters had no eggs) revealed homozygous frameshift mutations inherited in an autosomal recessive mode, which led to premature stop codon and resulted in a truncated ZP1 (404 aa residues), which was postulated to sequester ZP3 in the cytoplasm and prevented the formation of ZP matrix (Huang et al., 2014).