Gpr37l1 deficiency affects Shh signalling at the primary cilium in cultured murine cerebellar astrocytes

Cerebellar Purkinje neurons and Bergmann astrocytes express primary cilia from P0 to adulthood. The G-protein coupled receptor 37-like 1 (Gpr37l1) was identified as a modulator of brain primary ciliogenesis and is specifically expressed in Bergmann glia cells. During postnatal cerebellar development, the receptor protein interacts with the Ptch1 component of the cilium-associated sonic hedgehog (Shh) receptor complex. Genetic ablation of Gpr37l1 in mouse has specific effects on Shh-induced developmental signalling, with precocious proliferation and altered post-mitotic differentiation of external granule neuron precursors. It also alters the maturation of Bergmann glia fibres, which parallels the early layering of Purkinje neurons and differentiation of their dendritic arborisation. We are now studying the functional interaction among Gpr37l1 and Shh signalling pathway components in cultured models of cerebellar astrocytes, derived from Gpr37l1 null mutant or wild-type pups. Primary astrocyte cell cultures were prepared from cerebella of P7 Gpr37l1 null mutant or wild-type pups. Proliferative response to Shh was measured by BrdU incorporation, while differentiation was monitored by immunofluorescence with specific markers. Primary cultures treated with agonists or antagonists of the Shh pathway were stained with antibodies against Arl13b, Smo, Ptch1 and the specific analysis of Smo/Ptch1 localization was carried out.