ABSTRACT Developmental stuttering is a common speech disorder characterized by prolongations, blocks, and repetitions of speech sounds. Studies of developmental stuttering within twin, family, and population isolates suggest a strong genetic influence on stuttering risk with heritability estimates ranging from 0.42 to 0.84. Population-wide studies suggest that stuttering genetic risk factors are complex and involve both familial and population-level variation. In the largest genome-wide association study (GWAS) of stuttering, we identified 57 unique genome- wide significant loci associated with self-reported stuttering risk. Despite these population and familial efforts, the functional role that genetic variation contributes to stuttering risk remains largely uncharacterized. The current work proposes to use extant self-report stuttering GWAS results and newly genotyped and sequenced whole- exome data to better understand the biological mechanisms contributing to stuttering risk. Aim 1 will explore the genetically regulated gene expression associated with self-reported stuttering by leveraging GWAS summary statistics in over 1.1 million cases and controls. We will perform sex- and ancestry-specific transcriptome-wide association analyses using Joint-Tissue Imputation, prioritizing brain and neuromuscular tissues. We will assess consistency and generalizability of the genetically regulated gene expression associated with self-reported stuttering in independent sex- and ancestry- specific analyses in two independent cohorts - the International Stuttering Project and the Adolescent Health study. To explore the role of rare functional variation, Aim 2 will pinpoint familial genetic effects of developmental stuttering. Using array and whole- exome sequenced data collected in over 200 families, we will perform a novel polygenic risk-adjusted multipoint linkage analysis approach, conduct transmission disequilibrium tests, apply a pedigree variant annotation analysis search tool (pVAAST), and meta-analyze rare and common gene-based results developed in Aim 1. Aim 3 will identify neural endophenotypes related to stuttering-associated genes. We will utilize a newly developed tool, NeuroimaGene, to assess the genetic relationship between stuttering associated genes from Aims 1, 2, and the literature with neural endophenotypes measured in more than 33,000 people in the UKBiobank. Results from Aim 3 will illuminate specific neural mechanisms contributing to stuttering risk via genetic mechanisms and will be compared to results from the literature on brain imaging in people who stutter. Together, these aims will characterize functional relationships contributing to stuttering risk, better inform our understanding of stuttering, as well as potentially inform clinical and therapeutic practices.