COLOR CODE FOR N2 LAS4

April 20, 2012

DHH interpretation

This wild type adult hermaphrodite was laser-ablated to kill (how many? All?) vulval precursor cells (VPCs) during early larval life. The animal was then allowed to grow to adulthood, after which the animal was processed for electron microscopy. Within the present EM prints, there is no sign of any germline tissue, and I believe we are viewing the posterior midbody. There appear to be 16 immature muscle cells marked in the prints, eight clustered on the dorsal left, eight on the ventral right. They are the likely daughters of M.dl (which normally should migrate slightly forward and become integrated into the dorsal bodywall as bodywall muscle cells), and of M.vr (which ought to migrate anteriorward to the vulval region to become sex muscles). The laser ablation here seemingly has eliminated the entire germline and caused many daughters of the M mesoblast to become stranded without executing their normal cell fates.

An alternative possibility: in the absence of the normal germline, some cell fate switches have occurred among the immediate daughters of the M mesoblast, so that all new bodywall muscles have still been formed, but that all sex muscles have been stranded without migrating forward. Compare to Figure 10, Hedgecock et al., 1987.

Note that each marked cell has distinctive myofilaments within the cytoplasm, but never ordered into sarcomeres. . Thin sectioning and electron microscopy was conducted by Doug Kershaw at MRC, and cells were marked on prints by Eileen Southgate.

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