Rcan2 increases food intake and plays an important role in the development of age- and diet- induced obesity in male mice. However, in females, wild-type mice grow almost at a similar rate as Rcan2−/− mice on normal chow diet from 6 weeks of age. Here we showed that the ability of Rcan2 to promote weight gain was attenuated by energy expenditure mediated by 17β-estradiol in female mice. Using ovariectomy-operated models, we found that 17β-estradiol deprivation did not alter food intake, but induced more weight gain in wild-type mice than Rcan2−/− mice. If wild-type mice ingested equally as Rcan2−/− mice, in the same ovarian state they exhibited similar weight changes, but the mice in ovariectomized groups were significantly heavier than the ovarian-intact mice, suggesting that body weight is not only regulated by Rcan2, but also by 17β-estradiol. Furthermore, we demonstrated that Rcan2 and 17β-estradiol independently regulated body weight even on high-fat diets. Therefore, our findings indicate that Rcan2 and 17β-estradiol regulate body weight through different mechanisms. Rcan2 increases food intake, whereas 17β-estradiol promotes energy expenditure. These findings provide novel insights into the sexual dimorphism of body weight regulation.

Lgl1 was initially identified as a tumour suppressor in flies and is characterised as a key regulator of epithelial polarity and asymmetric cell division. A previous study indicated that More-Cre-mediated Lgl1 knockout mice exhibited significant brain dysplasia and died within 24h after birth. To overcome early neonatal lethality, we generated Lgl1 conditional knockout mice mediated by Pax2-Cre, which is expressed in almost all cells in the cerebellum, and we examined the functions of Lgl1 in the cerebellum. Impaired motor coordination was detected in the mutant mice. Consistent with this abnormal behaviour, homozygous mice possessed a smaller cerebellum with fewer lobes, reduced granule precursor cell (GPC) proliferation, decreased Purkinje cell (PC) quantity and dendritic dysplasia. Loss of Lgl1 in the cerebellum led to hyperproliferation and impaired differentiation of neural progenitors in ventricular zone. Based on the TUNEL assay, we observed increased apoptosis in the cerebellum of mutant mice. We proposed that impaired differentiation and increased apoptosis may contribute to decreased PC quantity. To clarify the effect of Lgl1 on cerebellar granule cells, we used Math1-Cre to specifically delete Lgl1 in granule cells. Interestingly, the Lgl1-Math1 conditional knockout mice exhibited normal proliferation of GPCs and cerebellar development. Thus, we speculated that the reduction in the proliferation of GPCs in Lgl1-Pax2 conditional knockout mice may be secondary to the decreased number of PCs, which secrete the mitogenic factor Sonic hedgehog to regulate GPC proliferation. Taken together, these findings suggest that Lgl1 plays a key role in cerebellar development and folia formation by regulating the development of PCs.

Abstract:It is widely accepted that body weight and adipose mass are tightly regulated by homeostatic mechanisms, in which leptin plays a critical role through hypothalamic pathways, and obesity is a result of homeostatic disorder. However, in C57BL/6J mice, we found that Rcan2 increases food intake and plays an important role in the development of age-and diet-induced obesity through a leptin-independent mechanism. RCAN2 was initially identified as a thyroid hormone (T3)-responsive gene in human fibroblasts. Expression of RCAN2 is regulated by T3 through the PI3K-Akt/PKB-mTOR-Rps6kb1 signaling pathway. Intriguingly, both Rcan2 −/− and Rps6kb1 −/− mutations were reported to result in lean phenotypes in mice. In this study we compared the effects of these two mutations on growth and body weight in C57BL/6J mice. We observed reduced body weight and lower fat mass in both Rcan2 −/− and Rps6kb1 −/− mice compared to the wild-type mice, and we reported other differences unique to either the Rcan2 −/− or Rps6kb1 −/− mice. Firstly, loss of Rcan2 does not directly alter body length; however, Rcan2 −/− mice exhibit reduced food intake. In contrast, Rps6kb1 −/− mice exhibit abnormal embryonic development, which leads to smaller body size and reduced food intake in adulthood. Secondly, when fed a normal chow diet, Rcan2 −/− mice weigh significantly more than Rps6kb1 −/− mice, but both Rcan2 −/− and Rps6kb1 −/− mice develop similar amounts of epididymal fat. On a high-fat diet, Rcan2 −/− mice gain body weight and fat mass at slower rates than Rps6kb1 −/− mice. Finally, using the double-knockout mice (Rcan2 −/− Rps6kb1 −/− ), we demonstrate that concurrent loss of Rcan2 and Rps6kb1 has an additive effect on body weight reduction in C57BL/6J mice. Our data suggest that Rcan2 and Rps6kb1 mutations both affect growth and body weight of mice, though likely through different mechanisms.