AHI1 gene

Overview

Gene (OMIM no.)
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.)
Inheritance
  • Autosomal recessive
Ocular features
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 diagnosisNext generation sequencing
  • Targeted gene panels (retinal)
  • Whole exome sequencing
  • Whole genome sequencing
ManagementOcularSystemic
  • Multidisciplinary approach
Therapies under research
  • None at present
Further information

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References

  1.  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
  2.  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
  3.  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
  4.  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
  5.  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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