The chromosomal signal for sex determination in Caenorhabditis elegans

In Caenorhabditis elegans, sex is determined by the number of X chromosomes which, in turn, determines the expression of the X-linked gene xol-1. Recent work has shown that xol-1 expression is controlled by least two distinct regulatory mechanisms, one transcriptional and another post-transcriptional. The transcriptional regulator is a repressor acting in XX embryos; although the specific gene has not been identified, the chromosome region has been defined. A previously defined regulator of xol-1, known as fox-1, maps to a different region of the X chromosome and works post-transcriptionally, consistent with the identification of the fox-1 gene product as a putative RNA binding protein.