Lineage‐specific requirements of Alx4 function in craniofacial and hair development

Abstract

<h3>Background</h3><p>Disruption of <em>ALX4</em> causes autosomal dominant parietal foramina and autosomal recessive frontonasal dysplasia with alopecia, but the mechanisms involving ALX4 in craniofacial and other developmental processes are not well understood. Although mice carrying distinct mutations in <em>Alx4</em> have been previously reported, the perinatal lethality of homozygous mutants together with dynamic patterns of <em>Alx4</em> expression in multiple tissues have hindered systematic elucidation of the cellular and molecular mechanisms involving Alx4 in organogenesis and disease pathogenesis.</p><h3>Results</h3><p>We report generation of <em>Alx4</em>^<em>f/f</em> conditional mice and show that tissue-specific Cre-mediated inactivation of <em>Alx4</em> in cranial neural crest and limb bud mesenchyme, respectively, recapitulated craniofacial and limb developmental defects as found in <em>Alx4</em>-null mice but without affecting postnatal survival. While <em>Alx4</em>-null mice that survive postnatally exhibited dorsal alopecia, mice lacking <em>Alx4</em> function in the neural crest lineage exhibited a highly restricted region of hair loss over the anterior skull whereas mice lacking <em>Alx4</em> in the cranial mesoderm lineage exhibited normal hair development, suggesting that Alx4 plays partly redundant roles in multiple cell lineages during hair follicle development.</p><h3>Conclusion</h3><p>The <em>Alx4</em>^<em>f/f</em> mice provide a valuable resource for systematic investigation of cell type- and stage-specific function of ALX family transcription factors in development and disease.</p>