Phosphatase PTEN in chicken muscle is regulated during ontogenesis.

The phosphatase and TENsin homolog deleted on chromosome 10 (PTEN) is a lipid and protein phosphatase able to inhibit significant actors of cell signaling (i.e. phosphatidylinositol-3'kinase and mitogen-activated protein kinase pathways). The aim of this study was to characterize PTEN and to investigate its regulation during ontogenesis in chicken muscle. Pectoralis major muscle was sampled on day 18 of the embryonic period (E18), at hatching (d0) and in fed chickens at 2, 7 and 43 days after hatching (d2, d7 and d43). We first cloned the totality of chicken PTEN cDNA; its translation into a putative protein showed more than 95% sequence identity with that characterized in mammals (humans, mice). PTEN was expressed under two major transcripts in the majority of tissues, including muscles where the expression of PTEN mRNA increased with age (P < 0.05). Surprisingly, the protein levels of PTEN (protein characterized with an apparent molecular weight of 55kDa) and its activity were considerably decreased between the E18 and d43 stages (approximately 8-10-fold reduction, P < 0.001). An association between these decreases and higher phosphorylation levels of two potential indirect downstream targets of phosphatase (i.e. AKT and ERK) was observed only in the early growth phases. It was concluded that phosphatase PTEN was expressed in chicken muscle and that its expression was regulated during ontogenesis.