shiva swamynathan [email protected] eye development and gene expression
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Why study eye development & gene expression?
Aniridia PAX6
Anophthalmia SOX2Iridocorneal FusionMicrophthalmia PAX6, OTX2, CHX10 & RAX
Keratolenticular Fusion
Opaque Cornea
Axenfeld-Rieger Syndrome PITX2
Peters AnomalyFOXC1, PAX6, PITX2, or CYP1B1
Anophthalmia RAX
Cell lineage during vertebrate eye development
Drosophila eye transcriptome
transcription factor genes are highly expressed
Structural and pigment biosynthesis genes
genes involved in intracellular signaling, neurotransmission, and the visual process
Whitney Heavner and Larysa Pevny. 2012. Cold Spring Harb Perspect Biol 2012;4:a008391
Transcription factor network that establishes the eye field
Gene expression in the developing optic vesicle
Transcription factors regulating corneal development
Swamynathan, S.K. 2013. J. Ophthalmol. 103947. PMID: 23533700
Mature cornea is formed by 8-10 weeks after birth
E12.5 E14.5 E16.5
E17.5 E18.5 Adult
Number of differentially regulated genes in the cornea between different time points
Stephens et al 2013. J. Bio. Chem. 288:34304-24
Cornea derives cells from the surface ectoderm and neural crest mesenchyme
Swamynathan, S.K. 2013. J. Ophthalmol. 103947. PMID: 23533700
KLF4IRF1ELF3Ets homologous factorHEBKLF5JunBRev-erbA-aIRF6Oxysterols receptor LXR-bPax6
Transcription Factors in the Mouse Cornea
Highly expressed in the cornea
Norman et al. 2004. IOVS. 45: 429-40 PMID: 14744882
Swamynathan et al., 2007. Mol. Cell. Biol. 27:182-194Kenchegowda et al 2011. Dev. Biol. 356:5-18
Wild Type Klf4CN
Functions of Klf4 and Klf5 in the ocular surface
Wild Type Klf5CN
Gene, transcript and protein structure of Pax6
Pax6 regulatory networks during early eye development
Neuroectoderm lineage Surface ectoderm lineage
Pax6 is essential for normal corneal development
Ramaesh et al., 2005. Exp.Eye Res. 81: 224-35
Mort et al. 2011. PMID: 22220198
Corneal functions of Pax6 are dosage-dependent
Role of Pitx2 in corneal development
Gage et al. 2014. Dev Dyn. PMID: 25044936
Paired-like homeodomain transcription factor PITX2 in E14.5 P42
PITX2 MutantsOverabundance of mesenchymeMalformed stroma and endotheliumAbsence of anterior chamberCorneo-lenticular fusion
Pitx2 helps establish corneal avascularity
Gage et al. 2014. Dev Dyn. PMID: 25044936
Corneal epithelium and the lens are both derived from the head surface ectoderm
Surface Ectoderm forms the Lens & the Corneal Epithelium
Lens and Cornea Share Transcriptional Networks
Genetic pathways inducing lens differentiation
Pax6 and Sox2 cooperatively regulate chicken δ1-crystallin gene expression
Kamachi et al 2001. Genes Dev. 15: 1272-86
Sox2 regulates cell-specific target genes through distinct partner factors
Kamachi et al 2001. Genes Dev. 15: 1272-86
Organization of retinal circuits
Whitney Heavner and Larysa Pevny. 2012. Cold Spring Harb Perspect Biol 2012;4:a008391
Transcription factors regulating temporal progression of mouse retinogenesis
Stages of photoreceptor development
OTX2 plays an essential role in vertebrate retinogenesis
Otx2-/- WT Otx2-/- WT
PN 0 PN 9
Otx2-/- WT
Otx2 expression indeveloping retina
E12.5
E17.5
PN6
Temporal functions of Otx2 in the mouse retina
OTX2 mutations are associated with blinding ocular defects and brain abnormalities
OTX2 gene network in the developing retina
Rx expression, phenotypes and regulation
overexpression
Xen
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Mou
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Xen
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Hum
an
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Essential roles of LHX2 in eye development
• Lhx2 is a LIM domain (a double-zinc finger motif found in a variety of proteins)- containing homeobox gene expressed in B-cells, forebrain and neural retina
• LHX2 coregulates the expression of Pax6, Six3 and Rax in the optic vesicle
• LHX2 is essential for eye development
Human NRL gene and protein
Nrl is required for rod photoreceptor development
Optic vesicle and RPE specification
MITF: A big gene associated with small eyes
Summary• Large-scale expression studies suggest that about a thousand genes are
expressed in a preferential manner in the eye, compared with the rest of the body• A series of homeobox transcription factors including Otx2, Sox2, Lhx2, Rax and
Pax6 play a major role in different stages of eye development • Eyefield is specified in early embryos by overlapping expression of Otx2 and Sox2
in the neural ectoderm, which in turn activate expression of Lhx2, Rax and Pax6, resulting in the formation of the optic vesicle
• Inductive interaction between neural ectoderm and surface ectoderm results in formation of the lens placode, defined by the expression of Pax6 and Sox2
• Lens and cornea share many transcriptional networks, consistent with their origin from the surface ectoderm
• Pitx2 and Foxc1 play major roles in anterior segment formation• Sox2 regulates cell-specific target genes by cooperating with distinct factors such
as Pax6, Oct3/4 and Brn2• Pax6 plays a major role in early retinogenesis, and formation of lens and cornea. • Cone cells are the default photoreceptor cell type. NRL expression is essential for
rod cell formation• Mitf plays a critical role in RPE formation
Expression of homeobox genes in the mature vertebrate retina