The Family Links Maternal Germline Sex to Embryonic Viability in .

The germline sex determination pathway in determines whether germ cells develop as oocytes or sperm, with no previously known effect on viability. The family of microRNAs are expressed in the germline and embryo and are essential for both viability and normal hermaphroditic sex determination, preventing aberrant male gene expression in XX hermaphrodite embryos. Here we show that combining feminizing mutations with partial loss of function of the family results in enhanced penetrance embryonic lethality that preferentially kills XO animals.