Categories: Craniofacial phene

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal recessive

Disease-related: yes

Key variant known: no

Species-specific description: see also OMIA 000240-9031 : Crest in Gallus gallus

History: As noted by Li et al., (2021), "Chicken skulls with cerebral hernia have been found at various archeological sites in Western Europe (Great Britain, Austria, Germany, and Hungary) from the Roman to the Post-Medieval period (Gál et al. 2010)". As recorded by Charles Darwin (1868) in volume 1 of his book "The Variation of Animals and Plants under Domestication", the "large, rounded crest of feathers" on the head of Polish chickens is "supported on a hemispherical protuberance of the frontal bones, which includes the anterior part of the brain." In other words, as noted by Li et al. (2021), Darwin is saying that the crest trait (OMIA 000240-9031) is associated with cerebral hernia. Among the breeds within the Crested category listed by Darwin were Sultans (Turkish), Crève-cœur (French) and Houdan (French). Darwin's words were summarised by Li et al. (2021) as "the cerebral hemispheres were extruded into the spherical region of the skull and the anterodorsal part of the skull is expanded into a large spherical protuberance." As described by Li et al. (2021), this association between crest and cerebral hernia has also been noted by Davenport (1906), Fisher (1934), Warren and Hutt (1936), Shelton (2010), Frahm and Rehkämper (1998), and Yoshimura et al. (2012).

Inheritance: Yoshimura et al. (2012) reported single-locus autosomal recessive inheritance in the crested Polish chicken. As also noted by Li et al. (2021), "No mutation responsible for cerebral hernia has yet been identified (Verdiglione and Rizzi 2018). It has been proposed that crest and cerebral hernia are determined by the same locus, or two closely linked loci (Davenport 1906; Fisher 1934; Warren and Hutt 1936; Bartels 2003)."

Markers: In reporting a 197bp duplication on chromosome GGA33 as a likely causal variant for Crest in chickens (OMIA 000240-9031), Li et al. (2021) noted that "the 197 bp duplication is required for the development of a large crest and susceptibility to cerebral hernia because only crested chicken show this malformation. However, this mutation is not sufficient to cause herniation because this malformation is not present in breeds with a small crest, like Silkie chickens."

Breed: Crested (Chicken) (VBO_0016845).
Breeds in which the phene has been documented. (If a likely causal variant has been documented for the phene, see the variant table breeds in which the variant has been reported).