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Expr2562
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Another notable aspect of ceh-13 expression in ray complexes 5, 7, and 9 was its cell-specific regulation. At the beginning of L4, the highest levels of protein were present in A- and B-type neurons, intermediate levels in the support cells, and lowest levels in hypodermal cells. Protein levels were higher in hyp7 than in hyp5,9. Upon tail retraction, expression in hyp7 was transiently upregulated and maintained high until mid-L4. At this point, there was upregulation of expression in st5, 7, and 9 and downregulation in all neuroblasts, as well as in hyp7. During tail morphogenesis in late L4 and in the course of ray shaping, significant upregulation of cytoplasmic CEH-13::GFP reporter levels occurred in structural cells, particularly around the papillae. In tests for ceh-13 expression in the sensory rays, ray-specific CEH-13 and CEH-13::GFP expression was detected shortly after the L3 moult, concomitantly with completion of the last divisions of the precursor cells. The protein initially exhibited uniform cytoplasmic distribution, then rapidly accumulated in the nuclei. On the basis of the complex patterning and dynamics of expression, two aspects of activity could be defined. In the first, ceh-13 was expressed in the A-type neurons of all rays, although lower levels were seen in the ventral ray groups 2, 4, and 8. This expression persisted until mid-L4 and was switched off thereafter except in ray 9. Thus, with the exception of R9A, detectable levels of protein were no longer present in the A-type neurons by the time of ray morphogenesis and the emergence of papillae. In the second aspect, CEH-13 and CEH-13::GFP were specifically expressed in the dorsal ray groups 5, 7, and 9, where they were present in all cells after completion of the last division of the precursor cells. Detectable levels of protein rapidly disappeared from the hypodermal cells in groups 5 and 9 but persisted in the hypodermal cell of 7 until the beginning of tail retraction. Three other ceh-13-expressing cells, R(5,7,9).aap, underwent apoptotic cell death shortly after division of the anterior neuroblasts that generated them. Thus, at the beginning of tail retraction, remaining ceh-13 activity could be observed exclusively in ray groups 5, 7, and 9, i.e., in B-type neurons of 5 and 7, in the A-type neuron of 9, and in the structural cells of 5, 7, and 9. The first expression of CEH-13 in the male tail was detected during the third larval stage (L3) in B_gamma. Upon division of the B_gamma cell, the protein became equally distributed between the anterior and posterior daughters B_gamma.a and B_gamma.p, but subsequently disappeared in B_gamma.p. CEH-13 and CEH-13::GFP expression in B_gamma.a was accompanied by subcellular redistribution of the protein, with an increase in nuclear and a decrease in cytoplasmic accumulation. After division of B_gamma.a, CEH-13 exhibited exclusive nuclear localisation in the two daughters B_gamma.al and B_gamma.ar. Also during L3, sex independent expression of CEH-13 in the tail region could be observed in an asymmetric neuron tentatively identified as Ql.ap. In the L4, several additional unidentified expressing cells were observed. |
Expression was both cytoplasmic and nuclear, and the nuclear expression appeared stronger in the region of the nucleolus. |
