Autism spectrum disorders (ASDs) are common, heritable neurodevelopmental conditions. The genetic architecture of ASDs is complex, requiring large samples to overcome heterogeneity. Here we broaden coverage and sample size relative to other studies of ASDs by using Affymetrix 10K SNP arrays and 1,181 [corrected] families with at least two affected individuals, performing the largest linkage scan to date while also analyzing copy number variation in these families. Linkage and copy number variation analyses implicate chromosome 11p12-p13 and neurexins, respectively, among other candidate loci. Neurexins team with previously implicated neuroligins for glutamatergic synaptogenesis, highlighting glutamate-related genes as promising candidates for contributing to ASDs.

Mutations in the Leucine Rich Repeat Kinase 2 (LRRK2) gene, first described in 2004 have now emerged as the most important genetic finding in both autosomal dominant and sporadic Parkinson's Disease (PD). While a formidable research effort has ensued since the initial gene discovery, little is known of either the normal or the pathological role of LRRK2. We have created lines of mice that express human mutant wild-type (hWT) or G2019S Lrrk2 via bacterial artificial chromosome (BAC) transgenesis. In vivo analysis of the dopaminergic system revealed abnormal dopamine neurotransmission in both hWT and G2019S transgenic mice evidenced by a decrease in extracellular dopamine levels, which was detected without pharmacological manipulation. Immunopathological analysis revealed changes in localization and increased phosphorylation of microtubule binding protein tau in G2019S mice. Quantitative biochemical analysis confirmed the presence of differential phospho-tau species in G2019S mice but surprisingly, upon dephosphorylation the tau isoform banding pattern in G2019S mice remained altered. This suggests that other post-translational modifications of tau occur in G2019S mice. We hypothesize that Lrrk2 may impact on tau processing which subsequently leads to increased phosphorylation. Our models will be useful for further understanding of the mechanistic actions of LRRK2 and future therapeutic screening.

Granular dystrophy Groenouw type I (CDGG1), Reis-Bücklers (CDRB), lattice type I (CDL1) and Avellino (ACD) are four 5q31-linked human autosomal dominant corneal dystrophies. Clinically, they show progressive opacification of the cornea leading to severe visual handicap. The nature of the deposits remains unknown in spite of amyloid aetiology ascribed to the last two. We generated a YAC contig of the linked region and, following cDNA selection, recovered the beta ig-h3 gene. In six affected families we identified missense mutations. All detected mutations occurred at the CpG dinucleotide of two arginine codons: R555W in one CDGG1, R555Q in one CDRB, R124C in two CDL1 and R124H in two ACD families. This suggests, as the last two diseases are characterized by amyloid deposits, that R124 mutated kerato-epithelin (the product of beta ig-h3) forms amyloidogenic intermediates that precipitate in the cornea. Our data establish a common molecular origin for the 5q31-linked corneal dystrophies.

Tau is a microtubule-associated protein implicated in neurodegenerative tauopathies. Alternative splicing of the tau gene (MAPT) generates six tau isoforms, distinguishable by the exclusion or inclusion of a repeat region of exon 10, that are referred to as 3-repeat (3R) and 4-repeat (4R) tau, respectively. We developed transgenic mouse models that express the entire human MAPT gene in the presence and absence of the mouse Mapt gene and compared the expression and regulation of mouse and human tau isoforms during development and in the young adult. We found differences between mouse and human tau in the regulation of exon 10 inclusion. Despite these differences, the isoform splicing pattern seen in normal human brain is replicated in our mouse models. In addition, we found that all tau, both in the neonate and young adult, is phosphorylated. We also examined the normal anatomic distribution of mouse and human tau isoforms in mouse brain. We observed developmental and species-specific variations in the expression of 3R and 4R-tau within the frontal cortex and hippocampus. In addition, there were differences in the cellular distribution of the isoforms. Mice transgenic for the human MAPT gene exhibited higher levels of neuronal cell body expression of tau compared to wild-type mice. This neuronal cell body expression of tau was limited to the 3R isoform, whereas expression of 4R tau was more "synaptic like", with granular staining of neuropil rather than in neuronal cell bodies. These developmental and speciesspecific differences in the regulation and distribution of tau isoforms may be important to the understanding of normal and pathologic tau isoform expression.

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