Doctor of Philosophy, University Of Adelaide (2017)
Bachelor of Science, University Of Adelaide (2012)
Abnormal Cell Sorting Underlies the Unique X-Linked Inheritance of PCDH19 Epilepsy.
2018; 97 (1): 59–66.e5
X-linked diseases typically exhibit more severe phenotypes in males than females. In contrast, protocadherin 19 (PCDH19) mutations cause epilepsy in heterozygous females but spare hemizygous males. The cellular mechanism responsible for this unique pattern of X-linked inheritance is unknown. We show that PCDH19 contributes to adhesion specificity in a combinatorial manner such that mosaic expression of Pcdh19 in heterozygous female mice leads to striking sorting between cells expressing wild-type (WT) PCDH19 and null PCDH19 in the developing cortex, correlating with altered network activity. Complete deletion of PCDH19 in heterozygous mice abolishes abnormal cell sorting and restores normal network activity. Furthermore, we identify variable cortical malformations in PCDH19 epilepsy patients. Our results highlight the role of PCDH19 in determining cell adhesion affinities during cortical development and the way segregation of WT and null PCDH19 cells is associated with the unique X-linked inheritance of PCDH19 epilepsy.
View details for DOI 10.1016/j.neuron.2017.12.005
View details for PubMedID 29301106
Teneurin-3 controls topographic circuit assembly in the hippocampus.
2018; 554 (7692): 328–33
Brain functions rely on specific patterns of connectivity. Teneurins are evolutionarily conserved transmembrane proteins that instruct synaptic partner matching in Drosophila and are required for vertebrate visual system development. The roles of vertebrate teneurins in connectivity beyond the visual system remain largely unknown and their mechanisms of action have not been demonstrated. Here we show that mouse teneurin-3 is expressed in multiple topographically interconnected areas of the hippocampal region, including proximal CA1, distal subiculum, and medial entorhinal cortex. Viral-genetic analyses reveal that teneurin-3 is required in both CA1 and subicular neurons for the precise targeting of proximal CA1 axons to distal subiculum. Furthermore, teneurin-3 promotes homophilic adhesion in vitro in a splicing isoform-dependent manner. These findings demonstrate striking genetic heterogeneity across multiple hippocampal areas and suggest that teneurin-3 may orchestrate the assembly of a complex distributed circuit in the mammalian brain via matching expression and homophilic attraction.
View details for DOI 10.1038/nature25463
View details for PubMedID 29414938
Functional Equivalence of the SOX2 and SOX3 Transcription Factors in the Developing Mouse Brain and Testes.
Gene duplication provides spare genetic material that evolution can craft into new functions. Sox2 and Sox3 are evolutionarily-related genes with overlapping and unique sites of expression during embryogenesis. It is currently unclear whether SOX2 and SOX3 have identical or different functions. Here we use CRISPR/Cas9-assisted mutagenesis to perform a gene-swap, replacing the Sox3 ORF with the Sox2 ORF to investigate their functional equivalence in the brain and testes. We show that increased expression of SOX2 can functionally replace SOX3 in the development of the infundibular recess/ventral diencephalon and largely rescues pituitary gland defects that occur in Sox3 null mice. We also show that ectopic expression of SOX2 in the testes functionally rescues the spermatogenic defect of Sox3 null mice and restores gene expression to near normal levels. Together, these in vivo data provide strong evidence that that SOX2 and SOX3 proteins are functionally equivalent.
View details for DOI 10.1534/genetics.117.202549
View details for PubMedID 28515211
Pcdh19 Loss-of-Function Increases Neuronal Migration In Vitro but is Dispensable for Brain Development in Mice
Protocadherin 19 (Pcdh19) is an X-linked gene belonging to the protocadherin superfamily, whose members are predominantly expressed in the central nervous system and have been implicated in cell-cell adhesion, axon guidance and dendrite self-avoidance. Heterozygous loss-of-function mutations in humans result in the childhood epilepsy disorder PCDH19 Girls Clustering Epilepsy (PCDH19 GCE) indicating that PCDH19 is required for brain development. However, understanding PCDH19 function in vivo has proven challenging and has not been studied in mammalian models. Here, we validate a murine Pcdh19 null allele in which a β-Geo reporter cassette is expressed under the control of the endogenous promoter. Analysis of β-Geo reporter activity revealed widespread but restricted expression of PCDH19 in embryonic, postnatal and adult brains. No gross morphological defects were identified in Pcdh19(+/β-Geo) and Pcdh19(Y/β-Geo) brains and the location of Pcdh19 null cells was normal. However, in vitro migration assays revealed that the motility of Pcdh19 null neurons was significantly elevated, potentially contributing to pathogenesis in patients with PCDH19 mutations. Overall our initial characterization of Pcdh19(+/β-Geo), Pcdh19(β-Geo/β-Geo) and Pcdh19(Y/β-Geo)mice reveals that despite widespread expression of Pcdh19 in the CNS, and its role in human epilepsy, its function in mice is not essential for brain development.
View details for DOI 10.1038/srep26765
View details for Web of Science ID 000376875800001
View details for PubMedID 27240640
View details for PubMedCentralID PMC4886214