![]() ![]() Early histological studies indicated that lethal embryos have shown abnormalities in the vascular system, nervous system, limbs, and guts 5, 6. ![]() It has been demonstrated that homozygous Creeper embryos generally die on the fourth day of embryonic development, but a few can survive to late stages 4. The semi-lethal Creeper trait, first described in 1925, was mainly characterized by a pronounced shortness of the extremities (Achondroplasia, OMIA000006-9031) 2, 3. Many lethal mutations have been reported in chicken, but few of them have been cloned. Chicken has been used as an important model organism for developmental biology, immunology and microbiology, leading to several fundamental discoveries in biology 1. Monogenic traits make excellent models for linking phenotypes and genotypes. One critical issue in biology is to understand the mechanism underlying phenotype formation. Our findings unravel the genetic basis of the longstanding Creeper phenotype mystery in chicken as the same gene also underlies bone dysplasia in human and mouse, and thus highlight the significance of IHH in animal development and human haploinsufficiency disorders. We therefore suggest the deletion of IHH to be the causative mutation for the Creeper trait in chicken. ![]() Expression analysis showed a much lower expression of IHH in Creeper than wild-type chickens. Large scale segregation analysis demonstrated that the deletion of IHH was fully linked with early embryonic death and the Creeper trait. Our results indicated that the deletion of Indian hedgehog ( IHH) gene was only found in the whole-genome sequencing data of lethal embryos and Creeper chickens. Here we have utilized ultra-deep sequencing and extensive analysis for targeting causative mutation controlling the Creeper trait. ![]() However, the genetic basis of the Creeper trait remains unknown. This trait has been widely cited in the genetics and molecular biology textbooks for illustrating autosomal dominant semi-lethal inheritance over decades. The Creeper trait, a classical monogenic phenotype of chicken, is controlled by a dominant semi-lethal gene. ![]()
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