vulva development in c.elegans

• C. elegans is a multicellular microscopic nematode. (Round worm)
• C. elegans is a free living, transparent that lives in temperate soil.
• C. elegans is an unsegmented and pseudocoelomate  
• It has two sexes 1) Hermaphrodite 2) a male
• Most of the c. elegans are hermaphrodite (meaning that they have both male and female sex organs)
• They do self and cross fertilization 
• It is a first multicellular organisms whose genome are sequenced.
• C. elegans is a modal organism because 1) easy to culture 2) generation time is short (3 days) 3) their fertilization and development  can occur under laboratory condition.
• vulva responsible for egg laying and sperm receiving.
• vulva is made up of 22 cells.
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☆signaling pathway involve in vulva development -

• Vulva development in C. elegans involves a network of intercellular signaling, signal transduction and transcriptional regulation.
• The process begins with formation of six hypodermal precursor cells, Vulval Precursor Cells (VPCs) - numbered as  P3.P to P8,P
• Each of these six cells have the potential to contribute to the development of vulva by receiving the needed signals from other group of cells.
• The position information needed by the VPCs to get divided into the respective parts of the vulva, is provided by the cell called Anchor cell, which secretes Lin-3 protein, similar to Epidermal growth factors, in the absence of anchor cell, a vulva does not develop.
• Lin-3 protein forms a concentration gradient, having maximum effect on the nearby VPCs and less effect on far ones. P.6P being closest to the anchor cells receives the highest concentration of the protein and generates the central vulval cells. (Primary)
• The other two VPCs adjacent to it - P5.P and P7.P receive a lower amount of protein and hence, develop the lateral vulaval cells.  (Secondary)
• The other remaining VPCs - P3.P, P4.P and P8.P develop the hypodermis of the vulva.
• The Lin3 protein is received by the cell surface receptor tyrosine kinase, Let-23, present on the VPCs, and the signal is transferred to the nucleus through MAP kinase pathway
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