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V. A. Mcilvain; Novel Hmx1 Homeobox Gene Is Necessary for Normal Eye Morphogenesis. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1297.
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© ARVO (1962-2015); The Authors (2016-present)
To understand the molecular mechanisms of cone photoreceptor development, we cloned and characterized a novel transcription factor Hmx1 , which binds to the highly conserved promoter sequence of the red (LWS) opsin gene.
We utilized a yeast one-hybrid system with a Xenopus laevis retinal cDNA library and bait consisting of highly conserved LWS opsin promoter to clone Hmx1. Phylogenetic analysis of Hmx1 family genes was performed to confirm the identity of newly isolated gene. Temporal and spatial expression patterns were determined by RT-PCR and microscopy of immunolabled cryosections. Morpholino mediated knock down of transcription was performed to establish the role of Hmx1 in eye morphogenesis.
The full length AA sequence of the clone is most closely related to the Hmx1 gene of the Hmx family and shares 53% identity with human Hmx1 (94% identity in homeodomain). RT-PCR analysis of Hmx1 expression at different developmental stages showed its transcripts are present as early as embryonic stage 12 and the expression is maintained throughout adulthood. RT-PCR suggested the presence of two Hmx1 splice variants during eye morphogenesis, while only one splice variant is predominantly present after stage 40. Immunohistochemical analysis showed that Hmx1 is strongly expressed in the photoreceptor and ganglion cell layers as well as in a restricted portion of the inner nuclear layer. Morpholino mediated knockdown of Hmx1 resulted in abnormalities in eye morphogenesis.
These results identify a novel transcriptional regulator of eye morphogenesis and provide a basis for further study of the hierarchy of gene regulatory networks involved in photoreceptor differentiation.
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