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Gene Review

ALG9  -  ALG9, alpha-1,2-mannosyltransferase

Homo sapiens

Synonyms: Alpha-1,2-mannosyltransferase ALG9, Asparagine-linked glycosylation protein 9 homolog, CDG1L, DIBD1, Disrupted in bipolar disorder protein 1, ...
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Disease relevance of ALG9

  • The ALG9 defect found in the patient with CDG--who presented with developmental delay, hypotonia, seizures, and hepatomegaly--shows that efficient lipid-linked oligosaccharide synthesis is required for proper human development and physiology [1].
  • Inborn ALG9 deficiency (congenital disorders of glycosylation type IL) is associated with progressive microcephaly, seizures, developmental delay, and hepatomegaly [2].

Psychiatry related information on ALG9

  • It is unknown whether common variations of ALG9 predispose to bipolar affective disorder [2].
  • Gene content analyses of the breakpoint junctions revealed disruption of a gene (DIBD1 ) at 11q23, a genomic region that has also been implicated in schizophrenia and Tourette syndrome [3].

High impact information on ALG9

  • Using this approach, we have found, in a patient with CDG, a deficiency of the ALG9 alpha 1,2 mannosyltransferase enzyme, which causes an accumulation of lipid-linked-GlcNAc(2)Man(6) and -GlcNAc(2)Man(8) structures, which was paralleled by the transfer of incomplete oligosaccharides precursors to protein [1].
  • Identification and functional analysis of a defect in the human ALG9 gene: definition of congenital disorder of glycosylation type IL [1].
  • A homozygous point-mutation 1567G-->A (amino acid substitution E523K) was detected in the ALG9 gene [1].
  • These analyses overall failed to support a role for DIBD1 in disease susceptibility [3].
  • In vivo competition studies against (R,R)-[125I]IQNB indicate that DIBD crosses the blood brain barrier (BBB) [4].

Biological context of ALG9


Anatomical context of ALG9

  • A defect in the ALG9 enzyme was suggested by the accumulation of the DolPP-GlcNAc2Man6 and DolPP-GlcNAc2Man8 in the patient's fibroblasts and confirmed by mutation analysis: the patient is homozygous for the ALG9 mutation p.Y286C [5].
  • We conclude that a suitably radiolabeled derivative of DIBD may be of potential use in emission tomographic study of changes in m2 receptors in the central nervous system [4].
  • In vitro competition studies against [3H](R)-3-quinuclidinylbenzilate ([3H]QNB) and [3H]N-methylscopolamine ([3H]NMS), using membranes derived from transfected cells expressing only m1, m2, m3, or m4 receptor subtypes, indicate that DIBD is selective for m2/m4 over m1/m3 [4].

Analytical, diagnostic and therapeutic context of ALG9

  • In vivo rat brain dissection studies of the competition of PBID or DIBD against (R,S)[125I]IQNB or [3H]QNB exhibited a dose-dependent preferential decrease in the binding of the radiotracer in brain regions that are enriched in the m2 muscarinic subtype [6].


  1. Identification and functional analysis of a defect in the human ALG9 gene: definition of congenital disorder of glycosylation type IL. Frank, C.G., Grubenmann, C.E., Eyaid, W., Berger, E.G., Aebi, M., Hennet, T. Am. J. Hum. Genet. (2004) [Pubmed]
  2. Common variations in ALG9 are not associated with bipolar I disorder: a family-based study. Baysal, B.E., Willett-Brozick, J.E., Bacanu, S.A., Detera-Wadleigh, S., Nimgaonkar, V.L. Behavioral and brain functions [electronic resource] : BBF. (2006) [Pubmed]
  3. A mannosyltransferase gene at 11q23 is disrupted by a translocation breakpoint that co-segregates with bipolar affective disorder in a small family. Baysal, B.E., Willett-Brozick, J.E., Badner, J.A., Corona, W., Ferrell, R.E., Nimgaonkar, V.L., Detera-Wadleigh, S.D. Neurogenetics (2002) [Pubmed]
  4. A novel muscarinic receptor ligand which penetrates the blood brain barrier and displays in vivo selectivity for the m2 subtype. Gitler, M.S., Cohen, V.I., De la Cruz, R., Boulay, S.F., Jin, B., Zeeberg, B.R., Reba, R.C. Life Sci. (1993) [Pubmed]
  5. CDG-IL: an infant with a novel mutation in the ALG9 gene and additional phenotypic features. Weinstein, M., Schollen, E., Matthijs, G., Neupert, C., Hennet, T., Grubenmann, C.E., Frank, C.G., Aebi, M., Clarke, J.T., Griffiths, A., Seargeant, L., Poplawski, N. Am. J. Med. Genet. A (2005) [Pubmed]
  6. In vitro and in vivo m2 muscarinic subtype selectivity of some dibenzodiazepinones and pyridobenzodiazepinones. Cohen, V.I., Jin, B., McRee, R.C., Boulay, S.F., Cohen, E.I., Sood, V.K., Zeeberg, B.R., Reba, R.C. Brain Res. (2000) [Pubmed]
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