Cystathionine β‐synthase gene inactivation dysregulates major urinary protein biogenesis and impairs sexual signaling in mice

Reproductive success in mice depends on sexually dimorphic major urinary proteins (Mup) that facilitate interactions between females and males. Deletion of cystathionine β-synthase (Cbs) gene, a metabolic gene important for homeostasis of one-carbon metabolism, impairs reproduction by causing female infertility in mice. Here, we examined Mup biogenesis and sexual signaling in Cbs−/− versus Cbs+/− mice. We found significantly reduced levels of total urinary Mup protein in male and female Cbs−/− versus Cbs+/− mice. SDS-PAGE/Western blot, ESI-MS, and RT-qPCR analyses of the liver, plasma, and urinary proteins identified a male-specific Mup20 in Cbs−/−, but not in Cbs+/− females. The 18 893 Da Mup20 became the most abundant in urine of Cbs−/− females and males. Effects of Cbs genotype on 18 645 Da, 18 693 Da, and 18 709 Da Mup species abundance were Mup- and sex-specific. Cbs genotype-dependent changes in hepatic Mups and Mup20 expression were similar at the protein and mRNA level. Changes in Mups, but not in Mup20, can be explained by downregulation of hepatic Zhx2 and Ghr receptors in Cbs−/− mice. Behavioral testing showed that Cbs+/− females ignored Cbs−/− male urine but were attracted to Cbs+/− male urine. Cbs+/− males ignored urine of Cbs−/− males but countermarked urine of other Cbs+/− males and were attracted to urines of Cbs−/− as well as Cbs+/− females. Cbs−/− males did not countermark urine of Cbs+/− males but were attracted to urines of Cbs+/− females. Taken together, these findings show that Cbs, a metabolic gene, interacts with the processes involved in Mup biogenesis that are essential for the maintenance of sexual dimorphism and signaling and suggest that dysregulation of these interactions impairs reproductive fitness in mice.