Ron C. Michaelis

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Of the chronic mental disabilities of childhood, autism is causally least well understood. The former view that autism was rooted in exposure to humorless and perfectionistic parenting has given way to the notion that genetic influences are dominant underlying factors. Still, identification of specific heritable factors has been slow with causes identified(More)
Haplotype analysis was undertaken in 20 cases of 15q11-q13 deletion associated with Prader-Willi syndrome (PWS) or Angelman syndrome (AS) to determine if these deletions arose through unequal meiotic crossing over between homologous chromosomes. Of these, six cases of PWS and three of AS were informative for markers on both sides of the deletion. For four(More)
The genetic contribution to autism is often attributed to the combined effects of many loci (ten or more). This conclusion is based in part on the much lower concordance for dizygotic (DZ) than for monozygotic (MZ) twins, and is consistent with the failure to find strong evidence for linkage in genome-wide studies. We propose that the twin data are(More)
Congenital hydrocephalus associated with aqueductal stenosis and/or agenesis of the corpus callosum has been described in newborn males with mutations in L1CAM, a gene that encodes a neural cell adhesion molecule. These males usually have severe mental retardation and may have spastic paraplegia and adducted thumbs. In contrast, Hirschsprung disease, or(More)
Townes-Brocks syndrome is an autosomal dominantly inherited disorder, which comprises multiple birth defects including renal, ear, anal, and limb malformations. TBS has been shown to result from mutations in SALL1, a human gene related to the developmental regulator SAL of Drosophila melanogaster. The SALL1 gene product is a zinc finger protein thought to(More)
Autistic disorder is a neurodevelopmental disorder with a complex genetic etiology. Observations of maternal duplications affecting chromosome 15q11-q13 in patients with autism and evidence for linkage and linkage disequilibrium to markers in this region in chromosomally normal autism families indicate the existence of a susceptibility locus. We have(More)
Twelve male Sprague-Dawley rats were trained in a two-choice, food reinforced, drug discrimination task utilizing 10 mg/kg cocaine and saline as discriminative stimuli. Subjects were tested for stimulus generalization with a wide range of cocaine doses and several dose combinations of caffeine, ephedrine, and phenylpropanolamine (CEP). Caffeine produced(More)
We present the clinical, cytogenetic, and molecular studies on a constitutional deletion of 19q ascertained prenatally due to decreased fetal activity and IUGR. Chromosome analysis by GTG banding on amniocytes suggested a del(19)(q13.1q13.3), but the analysis of microsatellites by PCR demonstrated that the deletion involved the distal segment of q12 and the(More)
Individuals with autism spectrum disorders (ASDs) have impairments in executive function and social cognition, with males generally being more severely affected in these areas than females. Because the dopamine D1 receptor (encoded by DRD1) is integral to the neural circuitry mediating these processes, we examined the DRD1 gene for its role in(More)
Recent studies have identified a (CCG)n repeat in the 5' untranslated region of the CBL2 protooncogene (11q23.3) and have demonstrated that expansion of this repeat causes expression of the folate-sensitive fragile site FRA11B. It has also been demonstrated that FRA11B is the site of breakage in some cases of Jacobsen syndrome (JS) involving terminal(More)