P&F Grant Awards

Year 11

Grant # 24

Genetic models of Chiari I malformation: Zebrafish models of CM1-associated genes

PI: Gabriel Haller, PhD


Specific Aims

Chiari type I malformation (CM1) is one of the most common pediatric neurological conditions, affecting ~3% of individuals undergoing brain imaging. CM1 is characterized by the herniation of the cerebellum through the foramen magnum into the spinal canal, often leading to obstruction of normal cerebrospinal fluid flow, compression of the brainstem and numerous neurological symptoms ranging from mild headaches to lifethreatening respiratory failure. The formation of CM1 is hypothesized to largely result from defects of musculoskeletal tissues in the base of the skull. There is a strong connection between adolescent idiopathic scoliosis (AIS) and the development of Chiari I malformation in children with approximately 20% of idiopathic CM1 cases presenting with concomitant severe scoliosis. This rate is notably much higher than the 3% population prevalence of scoliosis. Additionally, the rate of CM1 among patients with monogenic connective tissue disorders is significantly higher than in the general population with 12.7% of CM1 patients meeting criteria for Ehlers-Danlos syndrome or a related hereditary disorder of connective tissue.
We recently found a strong connection between genetic variation in genes related to connective tissue disorders (FBN1 and collagen genes) and scoliosis risk. Together with the epidemiological evidence connecting CM1 and scoliosis, this genetic data leads us to believe that CM1 and scoliosis may share underlying, largely musculoskeletal, etiology. We have now identified several genes enriched for deleterious protein-coding genetic variation among our cohort of 250 exome-sequenced CM1 patients compared to our large in-house cohort of control exome sequenced individuals (>3000 exome sequenced individuals). Several of the top CM1-associated genes have potential roles in the formation of the skull base or connective tissue development, including CUL7, ERCC6 and LAMC3. The goal of this proposed investigation is to determine the effects of disrupting these CM1-associated genes in zebrafish to understand their mechanisms of pathogenicity in humans. By creating directed mutations, knock-out of CM1-associated genes and knock-in of specific CM1-associated mutations, we will be able to determine the role of targeted genes in CM1 pathology and uncover the cellular and molecular etiology of CM1. The specific aims of this study are as follows:

Aim 1: Creation and characterization of zebrafish with genetic disruption of CM1-associated genes.
Aim 1A: Create knock-out zebrafish lines for CM1-associated genes and knock-in lines for evolutionarily conserved CM1-associated mutations using the Washington University zebrafish core facility with validation of mutant lines by next generation sequencing at the Genome Technology Access Center (WUSM).
Aim 1B: Measure skull and spine abnormalities in zebrafish mutants using both tissue-specific fluorescent zebrafish lines, bone/cartilage staining using the WU zebrafish core facility and by μ-CT imaging of mutant zebrafish at the Musculoskeletal Research Center (WUMRC).