BIOL130 Lecture Notes - Tx Network, Conjoined Twins, Pitx2
28 Jan 2013
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Expression is sensitive to retinoic acid (anterior end of cluster is more sensitive and therefore more easily activated by ra) 2. expressed in overlapping domains along the a/p axis. Hindbrain: discrete hox gene expression boundaries along borders of. Increases ra secretion as it moves anterior posterior. Notochord expresses shh neural tube floorplate induced. Shh (high levels of shh induce floor plate, low levels: motor neurons) Shh induces ventral neuronal cell types based on conc. **shh and wnt act in opposition to influence ventral and dorsal patterns, respectively** 1. situs inversus totalis everything on opposite side rare and not harmful. 2. heterotaxia heart and viscera orient independently. 3. isomerism duplicated right or left side identity conjoined twins: right side of left twin can affect development of left side of right twin, but not vice-versa. Lrd (left-right dynein) necessary for correct distribution of asymmetric protein expression (nodal, lefty, pitx2) mutants: 50% normal, 50% s. i. t. (kartager"s syndrome)
