No abstract

These findings indicate that a novel IMD gene exists on chromosome 18p11.

Multiple genes have been now identified as causing Parkinson's disease (PD). In 2003, two mutations were identified in exon 1 of the Nurr1 gene in 10 of 107 individuals with familial PD. To date, investigators have only focused on screening for these known mutations of the Nurr1 gene. All individuals were recruited from two Parkinson's disease clinics in Canada. Following PCR amplification of each exon of the Nurr1 gene, samples underwent denaturing high-performance liquid chromatography (DHPLC) analysis. Ten individuals also underwent direct sequencing as well as any samples where variants were identified. The Nurr1 gene was evaluated for 202 PD individuals, 37% of whom had at least one relative with PD and 100 control non-PD individuals. Using DHPLC and direct sequencing, we did not detect any sequence variants in exon 1. Variants in amplicon 6 were seen and direct sequencing confirmed a known NI6P polymorphism in intron 6. Novel polymorphisms were also identified in exon 3 and intron 5. A novel mutation was identified in exon 3 in one nonfamilial PD individual. This heterozygous C-to-G transversion resulted in a serine-to-cysteine substitution and was not identified in any of the other 602 chromosomes screened. Mutations in the Nurr1 gene in our large cohort of familial and sporadic PD individuals are rare. The novel mutation in exon 3 is predicted to affect phosphorylation and functional studies to assess this are underway. This is the first coding mutation identified in the Nurr1 gene for Parkinson's disease.

Human neural progenitor cells (hNPC) derived from the developing brain can be expanded in culture and subsequently differentiated into neurons and glia. They provide an interesting source of tissue for both modeling brain development and developing future cellular replacement therapies. It is becoming clear that hNPC are regionally and temporally specified depending on which brain region they were isolated from and its developmental stage. We show here that hNPC derived from the developing cortex (hNPC CTX ) and ventral midbrain (hNPC VM ) have similar morphological characteristics and express the progenitor cell marker nestin. However, hNPC CTX cultures were highly proliferative and produced large numbers of neurons, whereas hNPC VM divided slowly and produced fewer neurons but more astrocytes. Microarray analysis revealed a similar expression pattern for some stemness markers between the two growing cultures, overlaid with a regionally specific profile that identified some important differentially expressed neurogenic transcription factors. By overexpressing one of these, the transcription factor ASCL1, we were able to regain neurogenesis from hNPC VM cultures, which produced larger neurons with more neurites than hNPC CTX but no fully mature dopamine neurons. Thus, hNPC are regionally specified and can be induced to undergo neurogenesis following genetic manipulation. Although this restores neuronal production with a region-specific phenotype, it does not restore full neurochemical maturation, which may require additional factors.