AHI1 gene

Overview

Gene (OMIM no.)	AHI1 (#608894)
Function of gene/protein	Protein: Abelson helper integration site 1 Component of the primary cilia basal body Involved in formation of cilia and transport of vesicles Required for cerebellar and cortical development
Clinical phenotype (OMIM phenotype no.)	Joubert syndrome 3 (#608629)
Inheritance	Autosomal recessive
Ocular features	Oculomotor apraxia Nystagmus Strabismus Wide range of retinal dystrophies including retinitis pigmentosa and Leber congenital amaurosis
Visual function	Variable ocular phenotypes Poorer visual function in LCA patients
Systemic features	Neurological (hypotonia, ataxia and oculomotor apraxia, white matter abnormalities, polymicrogyria, corpus callosum abnormalities) Seizures may occur Neonatal breathing abnormalities Psychomotor delay Renal association uncommon but a case of early end stage renal failure due to nephronophthisis has been reported
Key investigations	Full-field and pattern ERG FAF and OCT MRI brain: characteristic “molar tooth sign” due to cerebellar vermis hypoplasia Renal ultrasound Assessment with a paediatrician and other relevant specialists
Molecular diagnosis	Next generation sequencing Targeted gene panels (retinal) Whole exome sequencing Whole genome sequencing
Management	Ocular Management of LCA/EOSRD Management of RP Systemic Multidisciplinary approach
Therapies under research	None at present
Further information	OMIM Genetic and Rare Disease Information Center

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References

Hsiao, Y.-C., Tong, Z.J., Westfall, J.E., Ault, J.G., Page-Mccaw, P.S. & Ferland, R.J. (2009) Ahi1, whose human ortholog is mutated in Joubert syndrome, is required for Rab8a localization, ciliogenesis and vesicle trafficking. Human Molecular Genetics, 18 (20), pp.3926–3941
Lagier-Tourenne C, Boltshauser E, Breivik N, et al. Homozygosity mapping of a third Joubert syndrome locus to 6q23. J Med Genet. 2004;41(4):273-277
Valente, E.M., Brancati, F., Silhavy, J.L., Castori, M., Marsh, S.E., Barrano, G., Bertini, E., Boltshauser, E., Zaki, M.S., Abdel-Aleem, A., Abdel-Salam, G.M.H., Bellacchio, E., Battini, R., Cruse, R.P., Dobyns, W.B., Krishnamoorthy, K.S., Lagier-Tourenne, C., Magee, A., Pascual-Castroviejo, I., Salpietro, C.D., Sarco, D., Dallapiccola, B. & Gleeson, J.G. (2006) AHI1gene mutations cause specific forms of Joubert syndrome-related disorders. Annals of Neurology, 59 (3), pp.527–534
Valente EM, Marsh SE, Castori M, et al. Distinguishing the four genetic causes of Jouberts syndrome-related disorders [published correction appears in Ann Neurol. 2005 Jun;57(6):934]. Ann Neurol. 2005;57(4):513-519
Utsch B, Sayer JA, Attanasio M, et al. Identification of the first AHI1 gene mutations in nephronophthisis-associated Joubert syndrome. Pediatr Nephrol. 2006;21(1):32-35

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Updated on November 30, 2020

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