Sonic hedgehog promotes somitic chondrogenesis by altering the cellular response to BMP signaling

Article Abstract:

Presomitic mesoderm (psm) cultured in the presence of Sonic hedgehog (Shh), a secreted signaling molecule involved in floor plate and notochord signals that promote chondrogenesis of the somitic mesoderm, will differentiate into cartilage. Later stages of the differentiation depend specifically on bone morphogenetic protein (BMP) signaling. Shh acts along with BMPs to induce cartilage and also changes competence of target cells to respond to BMPs. Without Shh, BMP administration brings on lateral plate gene expression in cultured psm. It seems that chondrogenesis of somitic tissues can be separated into two phases, one being Shh-mediated precursor cell generation, the other later exposure to BMPs. The precursor cells can start chondrogenesis, responding to BMP signaling. The BMPs trigger chondrogenic differentiation.

United States, Cellular signal transduction, Morphogenesis, Mesoderm, Cartilage cells

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Ectopic Pax-3 activates MyoD and Myf-5 expression in embryonic mesoderm and neural tissue

Article Abstract:

Immunohistochemistry and polymerase chain reaction were performed on specimens obtained from chick embryonic tissues to study the genetic regulation of myogenesis. The results showed that either signals from the overlying ectoderm or Wnt and Sonic hedgehog signals can induce somitic expression of the paired box transcription factors, Pax-3 and Pax-7, concomitant with the expression of Myf-5 and prior to that of MyoD. The findings also identified the retrovirus gene product Pax-3 as a key regulator of somitic myogenesis.

Analysis, Usage, Polymerase chain reaction, Striated muscle, Neural tube, Immunohistochemistry, Chick embryo

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Regulation of dorsal somitic cell fates: BMPs and Noggin control the timing and pattern of myogenic regulator expression

Article Abstract:

Somitic myogenesis is negatively regulated. Dorsal somitic cell fates and regulation have been studied. Time and place of myogenesis in the somite is regulated by variation in levels of BMP activity and localized expression of a BMP antagonist. Noggin, BMP antagonist, expressed lateral to the somite greatly expands MyoD expression into the lateral regions of the somite. It also represses Pax3 expression in the same tissue and brings on formation of a lateral myotome.

Genetic transcription, Transcription (Genetics), Cell cycle, Genetic translation, Translation (Genetics), Somite, Somites (Embryology)

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