How do gain of function genetic mutations impair craniofacial development?

Background:

Serious congenital anomalies, or birth defects, affect around 6% of all newborn babies each year and are the leading cause of infant mortality in developed countries. This project will focus on understanding the cause of abnormal development of the face and head (craniofacial anomalies), such as cleft lip and cleft palate, which are among the most common birth defects worldwide. Significant progress has been made towards identification of the genetic basis of these disorders, but there are large gaps in our knowledge, in part owing to the variety of possible causative genes, and the potential influence of environmental factors. Identification of the causative genes, the mechanisms by which they affect craniofacial development and the potential influence of nutrition or metabolic factors are essential for improved diagnosis and counselling and to make progress towards development of preventive therapies. Most studies of the genetics of craniofacial anomalies have focussed on loss of function mutations, whereas this project will build on our recent identification of gain of function (over-expression) mutations in specific genes which are expressed during craniofacial development.

Aims/Objectives:

This project will make use of a novel mouse model which displays craniofacial abnormalities of the palate and cranial bones. In this model, whole genome sequencing identified an insertional mutation in the promoter of a Grhl family transcription factor, which results in over-expression.

The overall aim of this project is to determine how gain of function mutations in Grhl disrupt craniofacial development. Objectives include (i) determining which cell types are responsible for abnormal development e.g. ectodermal versus mesodermal locations, (ii) carry out functional tests of the palate tissues to identify the cellular basis of failed fusion, (iii) to investigate the molecular mechanisms underlying abnormal development by identification of miss-regulated Grhl target genes, and (iv) to investigate possible means to normalise development and prevent Grhl related defects. These questions are directly relevant to the equivalent conditions in human patients.

Methods:

The project will provide training in a range of technologies, with a flexible approach allowing focus on the student’s interests. Core methods will be use of mouse genetic models, including conditional knockout/rescue by cre-lox technology (with a unique new mouse line), and lineage tracing with fluorescent reporters. Imaging will use light and fluorescent confocal microscopy using a range of technologies and analysis tools. Gene expression studies will provide training in RNA-seq approaches and bioinformatic analysis. Functional studies will provide an opportunity to learn organ explant culture and analysis of cellular proliferation, migration and adhesion.

References:
1.  Weinberg et al. PLoS Genet. 14: e1007438 (2018)
2.  Nikolopoulou et al. Nat. Comm. 10: 2487 (2019)
3.  Brouns et al. Hum. Mol. Genet. 20: 1536-1546 (2011)
4.  Ji et al. Birth Defects Res. 112: 1558-1587 (2020)