Germline stem cells are maintained in the distal region of the gonad. These cells undergo mitotic divisions and are maintained in this state through GLP-1 Notch signaling. The somatic distal tip cell (DTC) caps the end of the distal gonad and is essential for maintenance of the germline mitotic zone. As germ cells move away from the DTC they pass through the transition zone and enter early meiotic prophase. Here we present our work that identifies the Period protein homolog LIN-42 as a new regulator of germline development in C. elegans. Previous work in our lab and others has shown that LIN-42 is a transcription factor that regulates expression of both microRNAs and some mRNAs. LIN-42 is important for multiple developmental events including molting and hypodermal cell development. In addition, in the absence of LIN-42, late-stage specific events occur precociously in vulval precursor cells, sex myoblasts and the DTC. LIN-42 is expressed in all of these cells as well as multiple other cells in the muscles, neurons, intestines and hypodermis. Because of this we sought to understand the role of LIN-42, if any, in germline development. In
lin-42(
n1089) mutants we find that the mitotic zone size, determined by both the number of rows of cells and the total number of cells in the mitotic zone, is significantly reduced by 25% compared to wild type in young adult worms. We further find that mRNA levels of the GLP-1 Notch ligand,
lag-2, are significantly decreased in
lin-42(
n1089) mutant worms relative to wild type. Thus, LIN-42 likely impacts germline development by regulating LAG-2 expression and subsequent GLP-1 Notch signaling. Current work aims to determine if LIN-42 acts directly or indirectly to control
lag-2 levels. In Drosophila, the ATAXIN-2 protein is an important regulator of Period expression. In C. elegans, the ATAXIN-2 homolog
atx-2 promotes germline proliferation. We find that
lin-42 levels are significantly decreased in
atx-2 mutant worms relative to wild type, suggesting that ATX-2 impacts germline development in C. elegans at least in part through its affects on LIN-42. Altogether our results establish a new role for the conserved, important Period protein homolog LIN-42 in regulating early germline development.