<i>WeeT</i> mice have reduced peripheral CD4 and CD8 T cells due to <i>Mst1</i> deficiency.

<p><b>A</b>) Representation of CD4 and CD8 T cells, CD11b⁺ and B cells in the peripheral blood of <i>Mst1^wt</i> and <i>Mst1^h/h</i> mice. <b>B</b>) Inheritance of homozygous C57BL/6 (B), 129Sv/ImJ (C) or heterozygous (H) SNPs in F2 mice generated by crossing <i>Mst1^h/h</i> mice from the original C57BL/6 background to 129Sv/ImJ. Genetic mapping of T-lymphopenic (<i>WeeT</i>) and normal mice isolated a 4.5 Mb region on chromosome 2 harboring the causative mutation. <b>C</b>) <i>Mst1^h/h</i> mice harbor an A to C transversion in exon 5 of the <i>Mst1</i> gene, resulting in change of Leu₁₅₇ within the Mst1 kinase C-lobe to Arg (L₁₅₇R). <b>D</b>) Similar abundance of <i>Mst1</i> transcripts in wt and <i>Mst1^h/h</i> T cells. <b>E</b>) <i>Mst1^h/h</i> T cells have reduced Mst1 protein levels in the presence or absence of proteosome (MG132) or caspase-3 inhibitors (Z-DEVD).