ABSTRACT
Alternative splicing is a post-transcriptional process that greatly expands the proteomic and regulatory
complexity of metazoan genomes. Despite the rapid progress in uncovering the regulatory aspects of
alternative splicing, relatively little is known about their functional consequences. Understanding the
physiological relevance of alternative splicing, including its implication in human disease, is arguably one of the
most important unsolved problems in molecular biology. In this proposal, we will establish an approach to
systematically investigate the biological roles of alternatively spliced exons by focusing on unique activities that
these exons impart to proteins.
Alternative splicing plays a particularly prominent role in the nervous system, where it is required to
sustain the identities and functioning of a complex array of neuronal populations. This is reflected in the
growing list of complex brain disorders, including autism spectrum disorders (ASD), associated with known or
suspected splicing defects. A highly conserved program of neuronal microexons, defined as 3-27 nucleotide-
long exons, is misregulated in as many as a third of autism cases and recent findings indicate that deregulation
of microexon splicing can cause autism-like phenotypes in mice. We have identified a set of 24 transcriptional
regulators with switch-like regulation of microexons during early differentiation of human neurons. Among
these, we identified a suspected transcriptional factor and a candidate histone methyltransferase, PRDM10, as
an important regulator of early neurogenesis.
The goal of this proposal is to test the hypothesis that a switch-like inclusion of microexons,
specifically the PRDM10 e8 microexon, results in a switch in molecular activity that is critically
required during neuronal development. This is highly significant since deregulation of alternative
splicing of microexons can cause autistic-like behavior in mice and is linked to human
neurodevelopmental disorders, including ASD. Understanding the molecular basis of microexon
activity will help decipher how these tiny genetic elements regulate neuronal development.
We propose to test our hypothesis in two specific aims. First, we will investigate the mechanistic basis of
microexon-regulated molecular activity by inspecting the regulatory role of the e8 microexon spliced in the
neural isoform of PRDM10. We will combine biochemical and genetic approaches to examine transcriptional,
enzymatic, and protein-interacting properties of PRDM10 and their alteration upon microexon inclusion.
Second, we will interrogate the impact of the PRDM10 e8 microexon on neuronal function, in particular
synaptic signaling and activity-induced transcriptional responses. These studies will also establish a general
screening platform for investigating the impact of microexon perturbation on synaptic function.