regulation of somitogenesis

Definition

Target type: biologicalprocess

Any process that modulates the frequency, rate or extent of somitogenesis. [GOC:mtg_muscle]

Somitogenesis, the formation of somites, is a precisely regulated process that occurs during vertebrate embryogenesis. These paired blocks of mesoderm give rise to a variety of tissues, including skeletal muscle, vertebrae, and dermis. The regulation of somitogenesis involves a complex interplay of signaling pathways, transcription factors, and cellular processes.

**1. Segmentation Clock:** The segmentation clock is a molecular oscillator that establishes the periodic formation of somites. It involves a network of genes, primarily the *Hairy* and *Hes* genes, that oscillate in their expression levels in a rhythmic manner. These oscillations create a wave of gene expression that sweeps across the presomitic mesoderm (PSM), the region where somites form.

**2. Retinoic Acid (RA) Signaling:** RA is a morphogen that plays a crucial role in establishing the anterior boundary of each somite. RA is produced in the posterior PSM and diffuses anteriorly, creating a gradient that defines the region where somitogenesis will initiate.

**3. Wnt Signaling:** Wnt signaling is essential for the maintenance of the PSM and the regulation of somitogenesis. Wnt proteins are secreted from the posterior PSM and activate downstream signaling pathways that promote cell proliferation and prevent premature differentiation.

**4. Notch Signaling:** Notch signaling is involved in the segmentation of the PSM and the specification of somite cell fates. Notch signaling is activated by the interaction of Notch receptors on the cell surface with ligands expressed on neighboring cells. This interaction leads to the activation of downstream target genes, influencing cell fate decisions.

**5. FGF Signaling:** Fibroblast growth factors (FGFs) are involved in the regulation of somite size and the establishment of the anterior-posterior axis of the somite. FGF signaling is activated by FGF ligands produced in the PSM and surrounding tissues.

**6. Transcription Factors:** A variety of transcription factors, such as Pax3, Pax6, and Myf5, are involved in the specification of somite cell fates and the differentiation of different somite-derived tissues.

**7. Cell Migration and Epithelialization:** Cells within the PSM undergo directed migration and rearrangements to form the epithelial structure of the somite. This process is regulated by cell adhesion molecules, cytoskeletal proteins, and signaling pathways.

**8. Clock and Wavefront Model:** The regulation of somitogenesis is often described by the "clock and wavefront model," which integrates the roles of the segmentation clock, RA signaling, and other factors. The segmentation clock generates a periodic signal that is read by the moving wavefront of RA, setting the boundaries of each somite.'
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