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#vertebrate biology

2 public questions tagged with this topic.

Eye Lens Induction -l

Which factor is NOT involved in vertebrate lens formation?

Vertebrate lens regulatory network centers on Pax6, Sox2, Six3, Prox1, FoxE3 and L-Maf/c-Maf factors that directly control crystallin genes. Sox2 partners Pax6 on enhancers, L-Maf drives delta-crystallin, FoxE3 maintains anterior epithelium. HoxB1 belongs to posterior patterning Hox cluster controlling rhombomere identity in hindbrain and spinal cord via retinoic acid collinear expression. It does not express in anterior preplacodal ectoderm, never binds lens enhancers, and knockout shows hindbrain but not eye defects. Therefore Hox genes generally excluded from anterior sense placode development, distinguishing lens program from axial patterning modules.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 12: Lens transcription factors Pax6 Sox2 L-Maf versus Hox genes.

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Eye Lens Induction -ll

Which of the following is the primary inducer of vertebrate eye lens formation?

Vertebrate eye lens induction relies on optic vesicle as primary inducer of overlying head surface ectoderm. Optic vesicle evaginates from diencephalon, contacts competent head ectoderm expressing Pax6, and secretes BMP4 and FGF signals promoting lens placode thickening, invagination, and expression of Sox2, L-Maf, and crystallins. Lens placode is responding tissue, neural ectoderm becomes retina, surface ectoderm alone is not self-inductive. Classic Spemann and Lewis transplantation showed optic vesicle removal prevents lens while ectopic vesicle induces ectopic lens in competent regions and ages.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 12: Lens induction – optic vesicle as primary inducer.

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