title: Genetically determined low maternal serum dopamine beta-hydroxylase levels and the etiology of autism spectrum disorders.
abstract: Autism, a neurodevelopmental disability characterized by repetitive stereopathies and deficits in reciprocal social interaction and communication, has a strong genetic basis. Since previous findings showed that some families with autistic children have a low level of serum dopamine beta-hydroxylase (DbetaH), which catalyzes the conversion of dopamine to norepinephrine, we examined the DBH gene as a candidate locus in families with two or more children with autism spectrum disorder using the affected sib-pair method. DBH alleles are defined by a polymorphic AC repeat and the presence/absence (DBH+/DBH-) of a 19-bp sequence 118 bp downstream in the 5' flanking region of the gene. There was no increased concordance for DBH alleles in affected siblings, but the mothers had a higher frequency of alleles containing the 19-bp deletion (DBH-), compared to an ethnically similar Canadian comparison group (chi(2) = 4.20, df = 1, P = 0.02 for all multiplex mothers; chi(2) = 4.71, df = 1, P < 0.02 for mothers with only affected sons). Although the odds ratios suggested only a moderate relevance for the DBH- allele as a risk allele, the attributable risk was high (42%), indicating that this allele is an important factor in determining the risk for having a child with autism. DBH genotypes also differed significantly among mothers and controls, with 37% of mothers with two affected sons having two DBH- alleles, compared to 19% of controls (chi(2) = 5.81, df = 2, P = 0.03). DbetaH enzyme activity was lower in mothers of autistic children than in controls (mean was 23.20 +/- 15.35 iU/liter for mothers vs. 33.14 +/- 21.39 iU/liter for controls; t = - 1.749, df = 46, P = 0.044). The DBH- allele was associated with lower mean serum DbetaH enzyme activity (nondeletion homozygotes: 41.02 +/- 24.34 iU/liter; heterozygotes: 32.07 +/- 18.10 iU/liter; and deletion homozygotes: 22.31 +/- 13.48 iU/liter; F = 5.217, df = 2, P = 0.007) in a pooled sample of mothers and controls. Taken together, these findings suggest that lowered maternal serum DbetaH activity results in a suboptimal uterine environment (decreased norepinephrine relative to dopamine), which, in conjunction with genotypic susceptibility of the fetus, results in autism spectrum disorder in some families.
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario, Canada.
authors.forename: P D
authors.initials: PD
authors.lastname: Robinson
authors.forename: C K
authors.initials: CK
authors.lastname: Schutz
authors.forename: F
authors.initials: F
authors.lastname: Macciardi
authors.forename: B N
authors.initials: BN
authors.lastname: White
authors.forename: J J
authors.initials: JJ
authors.lastname: Holden
mesh_terms: D000483:Alleles; D001321:Autistic Disorder / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D004247:DNA / Q000737:chemistry / Q000235:genetics; D004252:DNA Mutational Analysis; D004299:Dopamine beta-Hydroxylase / Q000097:blood / Q000235:genetics*; D005190:Family; D005192:Family Health; D005838:Genotype; D016254:Mutagenesis, Insertional; D017384:Sequence Deletion
chemical_list: D004247:DNA; D004299:Dopamine beta-Hydroxylase