Analysis of ten candidate genes in autism by association and linkage

We studied the possible involvement of ten candidate genes in autism: proenkephalin, prodynorphin, and proprotein convertase subtilisin/kexin type 2 (opioid metabolism); tyrosine hydroxylase, dopamine receptors D2 and D5, monoamine oxidases A and B (monoaminergic system); brain‐derived neurotrophic factor, and neural cell adhesion molecule (involved in neurodevelopment). Thirty‐eight families with two affected siblings and one family with two affected half‐siblings, recruited by the Paris Autism Research International Sibpair Study (PARIS), were tested using the transmission disequilibrium test and two‐point affected sib‐pair linkage analysis. We found no evidence for association or linkage with intragenic or linked markers. Our family sample has good power for detecting a linkage disequilibrium of 0.80. Thus, these genes are unlikely to play a major role in the families studied, but further studies in a much larger sample would be needed to highlight weaker genetic effects. © 2002 Wiley‐Liss, Inc.