Tau isoform regulation is region- and cell-specific in mouse brain.

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, which 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 wildtype 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 species-specific differences in the regulation and distribution of tau isoforms may be important to the understanding of normal and pathologic tau isoform expression.

Heterogeneous association between engrailed-2 and autism in the CPEA network.

Autism is a neurodevelopmental disorder characterized by an early onset of abnormal social, communicative, and repetitive behavior. Engrailed-2 (EN2) was identified as an autism candidate gene because its influence on cerebellar development in mice parallels neurodevelopmental abnormalities seen in individuals with autism. Studies investigating association between markers at EN2 (chr7q36), a location associated with language disorders, and autism reveal mixed findings. Two positive reports revealed association with two intronic SNPs. Since the associated SNPs were in high linkage disequilibrium and shared similar minor allele frequencies, we chose to test whether one of the SNPs (rs1861972) was associated with autism in three recruiting sites from the NIH Collaborative Programs of Excellence in Autism (CPEA) network. A recessive model revealed significant association with broad autism spectrum disorder. Site specific analyses indicated differential allele transmission by site, despite similar ethnicity, and parental genotypes, suggesting the SNP may contribute to various risk haplotypes. No significant association with autism was found under an additive model for either a broad (autism spectrum disorder) or a narrow (autistic disorder) diagnostic group. Although our findings were not as robust as the previous studies, they suggest that rs1861972 may influence the risk for autism spectrum disorders. Future studies investigating EN2 should consider how the association of variants in this gene with autism could be influenced by differences in phenotype and possible interactions with genotypes at other autism candidate genes.

Genetic and immunologic considerations in autism.

According to recent epidemiological surveys, autistic spectrum disorders have become recognized as common childhood psychopathologies. These life-lasting conditions demonstrate a strong genetic determinant consistent with a polygenic mode of inheritance for which several autism susceptibility regions have been identified. Parallel evidence of immune abnormalities in autistic patients argues for an implication of the immune system in pathogenesis. This review summarizes advances in the molecular genetics of autism, as well as recently emerging concerns addressing the disease incidence and triggering factors. The neurochemical and immunologic findings are analyzed in the context of a neuroimmune hypothesis for autism. Studies of disorders with established neuroimmune nature indicate multiple pathways of the pathogenesis; herein, we discuss evidence of similar phenomena in autism.