Dataset Information

Disruption of ALX1 causes extreme microphthalmia and severe facial clefting: expanding the spectrum of autosomal-recessive ALX-related frontonasal dysplasia.

ABSTRACT: We present an autosomal-recessive frontonasal dysplasia (FND) characterized by bilateral extreme microphthalmia, bilateral oblique facial cleft, complete cleft palate, hypertelorism, wide nasal bridge with hypoplasia of the ala nasi, and low-set, posteriorly rotated ears in two distinct families. Using Affymetrix 250K SNP array genotyping and homozygosity mapping, we mapped this clinical entity to chromosome 12q21. In one of the families, three siblings were affected, and CNV analysis of the critical region showed a homozygous 3.7 Mb deletion containing the ALX1 (CART1) gene, which encodes the aristaless-like homeobox 1 transcription factor. In the second family we identified a homozygous donor-splice-site mutation (c.531+1G > A) in the ALX1 gene, providing evidence that complete loss of function of ALX1 protein causes severe disruption of early craniofacial development. Unlike loss of its murine ortholog, loss of human ALX1 does not result in neural-tube defects; however, it does severely affect the orchestrated fusion between frontonasal, nasomedial, nasolateral, and maxillary processes during early-stage embryogenesis. This study further expands the spectrum of the recently recognized autosomal-recessive ALX-related FND phenotype in humans.

SUBMITTER: Uz E

PROVIDER: S-EPMC2869009 | biostudies-literature | 2010 May

REPOSITORIES: biostudies-literature

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Disruption of ALX1 causes extreme microphthalmia and severe facial clefting: expanding the spectrum of autosomal-recessive ALX-related frontonasal dysplasia.

Uz Elif E Alanay Yasemin Y Aktas Dilek D Vargel Ibrahim I Gucer Safak S Tuncbilek Gokhan G von Eggeling Ferdinand F Yilmaz Engin E Deren Ozgur O Posorski Nicole N Ozdag Hilal H Liehr Thomas T Balci Sevim S Alikasifoglu Mehmet M Wollnik Bernd B Akarsu Nurten A NA

American journal of human genetics 20100506 5

We present an autosomal-recessive frontonasal dysplasia (FND) characterized by bilateral extreme microphthalmia, bilateral oblique facial cleft, complete cleft palate, hypertelorism, wide nasal bridge with hypoplasia of the ala nasi, and low-set, posteriorly rotated ears in two distinct families. Using Affymetrix 250K SNP array genotyping and homozygosity mapping, we mapped this clinical entity to chromosome 12q21. In one of the families, three siblings were affected, and CNV analysis of the cri ...[more]

PMID: 20451171

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Project description:The cellular and genetic mechanisms that coordinate formation of facial sensory structures with surrounding skeletal and soft tissue elements remain poorly understood. Alx1, a homeobox transcription factor, is a key regulator of midfacial morphogenesis. ALX1 mutations in humans are linked to severe congenital anomalies of the facial skeleton (frontonasal dysplasia, FND) with malformation or absence of eyes and orbital contents (micro- and anophthalmia). Zebrafish with loss-of-function alx1 mutations develop with craniofacial and ocular defects of variable penetrance, likely due to compensatory upregulation in expression of a paralogous gene, alx3. Here we show that zebrafish alx1;alx3 mutants develop with highly penetrant cranial and ocular defects that resemble human ALX1-linked FND. alx1 and alx3 are expressed in anterior cranial neural crest (aCNC), which gives rise to the anterior neurocranium (ANC), anterior segment structures of the eye and vascular pericytes. Consistent with a functional requirement for alx genes in aCNC, alx1; alx3 mutants develop with nearly absent ANC and grossly aberrant hyaloid vasculature and ocular anterior segment, but normal retina. In vivo lineage labeling identified a requirement for alx1 and alx3 during aCNC migration, and transcriptomic analysis suggested oxidative stress response as a key target mechanism of this function. Oxidative stress is a hallmark of fetal alcohol toxicity, and we found increased penetrance of facial and ocular malformations in alx1 mutants exposed to ethanol, consistent with a protective role for alx1 against ethanol toxicity. Collectively, these data demonstrate a conserved role for zebrafish alx genes in controlling ocular and facial development, and a novel role in protecting these key midfacial structures from ethanol toxicity during embryogenesis. These data also reveal novel roles for alx genes in ocular anterior segment formation and vascular development and suggest that retinal deficits in alx mutants may be secondary to aberrant ocular vascularization and anterior segment defects. This study establishes robust zebrafish models for interrogating conserved genetic mechanisms that coordinate facial and ocular development, and for exploring gene--environment interactions relevant to fetal alcohol syndrome.

Dataset Information

Disruption of ALX1 causes extreme microphthalmia and severe facial clefting: expanding the spectrum of autosomal-recessive ALX-related frontonasal dysplasia.

Publications

Disruption of ALX1 causes extreme microphthalmia and severe facial clefting: expanding the spectrum of autosomal-recessive ALX-related frontonasal dysplasia.

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