Project description:Epidermis is essential for animal survival, providing both a protective barrier and cellular sensor to the external environment. Interestingly, the epidermes of different species show broad morphological and functional diversity yet it is unclear whether this diversity came from modification of an existing gene regulatory network or de novo innovation of new genes. Here we identify the transcriptional regulators underlying the differentiation program of planarian epidermal lineage. We classify Smed-p53 as the most upstream molecule in this transcriptional cascade, suggesting a potentially conserved role for this gene in epidermal differentiation similar to TP63 in vertebrates. Moreover, we find that homologs of Sox and Pax family transcription factors, Smed-soxP-3 and Smed-pax-5, act cooperatively to activate the expression of epidermal markers. Together, these data show that planarian epidermal differentiation is regulated by a combination of conserved elements (p53/p63), recruitment of a non-conventional transcription module (soxP-3/pax-5), and novel genes (prog); they also suggest that specialized adpatations, such as epidermal mucus-secretion, arise from complex changes to gene networks. This experiment aims to identify regulators involved in epidermal differentiation at the neoblast stage by using RNA Seq to examine transcriptional changes in neoblasts (X1 population) isolated from animals treated with zfp-1 or p53 dsRNA.
Project description:Lipid metabolism is recognized as a key process for stem cell maintenance and differentiation but genetic factors that instruct stem cell function by influencing lipid metabolism remain to be delineated. Here we identify Tnfaip2 as an inhibitor of reprogramming of mouse fibroblasts into induced pluripotent stem cells. Tnfaip2 knockout embryonic stem cells (ESCs) exhibit differentiation failure and knockdown of the planarian orthologue, Smed-exoc3, abrogates in vivo differentiation of somatic stem cells, tissue homeostasis, and regeneration. Tnfaip2 deficient ESCs fail to induce synthesis of cellular triacylglycerol (TAG) and lipid droplets (LD) coinciding with reduced expression of Vimentin (Vim) – a known inducer of LD formation. Knockdown of Vim and Tnfaip2 act epistatically in enhancing cellular reprogramming of mouse fibroblasts. Similarly, planarians devoid of Smed-exoc3 displayed acute loss of TAGs. Supplementation of palmitic acid (PA) and palmitoyl-L-carnitine (a mitochondrial carrier of PA) restores the differentiation capacity of Tnfaip2 deficient ESCs as well as stem cell differentiation and organ maintenance in Smed-exoc3-depleted planarians. Together, these results identify a novel pathway, which is essential for stem cell differentiation and organ maintenance by instructing lipid metabolism.
