Embryonic expression profile of chicken CHD7, the ortholog of the causative gene for CHARGE syndrome.
BACKGROUND
CHARGE syndrome represents a constellation of malformations: C, coloboma of the iris or retina; H, heart defects; A, atresia of the choanae; R, retardation of growth and/or development; G, genital anomalies; and E, ear abnormalities. Recently, the Chromodomain helicase DNA-binding protein-7 (CHD7) at chromosome 8q12.1 was identified as a causative gene for CHARGE syndrome. Because CHD7 was identified as a causative gene using a positional cloning approach, the role of CHD7 in early embryogenesis needs to be further investigated.


METHODS
Fertilized chick eggs were incubated to Hamburger and Hamilton stages 4-20 and were studied using whole mount in situ hybridization. Chicken EST clones corresponding to the chicken CHD7 (cChd7) sequence were identified using the chicken EST sequence database. From the EST clones, a digoxigenin-labeled RNA probe was synthesized and hybridized in situ to the embryonic specimens.


RESULTS
The expression of cChd7 was pan-neuronal at stages 8-20. It was expressed throughout the rostral neural ectoderm and along the rostrocaudal axis but was absent from the more lateral, non-neuronal ectoderm. Adjacent to the neural tube, cChd7 transcripts were detected at the optic and otic placodes. At stage 20, cChd7 expression was observed in the branchial arches and olfactory placodes in addition to brain and optic and otic placodes.


CONCLUSIONS
cChd7 was expressed in the neural epithelium, the otic placodes, the optic placodes, the branchial arches, and the olfactory placodes, which are the primordial tissues that give rise to organs affected in human CHARGE syndrome patients.
Aramaki
Michihiko
M
Department of Pediatrics, Keio University School of Medicine, Tokyo, Japan.
Kimura
Tokuhiro
T
Udaka
Toru
T
Kosaki
Rika
R
Mitsuhashi
Takayuki
T
Okada
Yasunori
Y
Takahashi
Takao
T
Kosaki
Kenjiro
K
D000015:Abnormalities, Multiple / Q000196:embryology* / Q000235:genetics; D000818:Animals; D030161:Avian Proteins / Q000235:genetics / Q000378:metabolism*; D002642:Chick Embryo; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D047108:Embryonic Development; D005124:Eye Abnormalities / Q000196:embryology / Q000235:genetics; D006330:Heart Defects, Congenital / Q000196:embryology / Q000235:genetics; D006801:Humans; D017403:In Situ Hybridization; D008957:Models, Genetic; D008969:Molecular Sequence Data; D013577:Syndrome
D030161:Avian Proteins; D004268:DNA-Binding Proteins; D004265:DNA Helicases; C491434:CHD7 protein, human