Investigating sex differences in nuclear lamin levels and their impact on macrophage-regulated inflammation and severity of lamin linked disease

Biological sex is a major factor effecting degree and regulation of inflammation and immunity, yet the mechanisms involved remain largely unclear.

Nuclear envelope intermediate filament protein Lamin A plays a central role in determining cell behaviour, including inflammatory potential of macrophages, through mechanics and regulating gene expression. Lamin A has more disease-linked mutations than any other protein, and causes diseases from muscular dystrophies and lipodystrophies to premature-aging syndromes.

Lamin-linked muscular dystrophy generally presents earlier in males while the lipodystrophies present earlier and stronger in females, yet sex differences in Lamin A expression have not been investigated.

We recently observed sex differences in Lamin A levels in murine peritoneal macrophages. Lamin A expression in human blood monocytes is also sex-dependent. These exciting observations could explain stronger inflammatory responses but weaker infection resistance in males vs females and opens the possibility that lamin sex differences might explain dimorphisms in clinical presentation in nuclear

envelope-linked disorders.

This studentship will test the hypothesis that sex differences in lamin expression contribute to dimorphisms in immune cell function, inflammatory disease, and laminopathies. Aims 1. Characterise sex differences in lamin expression.

Lamin expression is influenced by the mechanical environment (e.g. tissue tension), but could also be influenced by cell-intrinsic (eg sex chromosome complement) and extrinsic (eg hormones/metabolism) effects of sex. These possibilities will be distinguished by determining how sex-dimorphisms in expression of lamin A in human monocyte-derived macrophages, patient myoblasts, and macrophages isolated across murine tissues are effected by culture on different tension substrates or in sexmatched/mismatched serum/tissue fluids.

Sex differences in Lamin expression will also be investigated in laminopathy patient-derived cells and bioinformatically by interrogating mRNA expression databases. 2. Test consequences of lamin A sex differences for macrophage function.

Lamin A levels will be modulated in vitro and in vivo to determine if stronger inflammatory responses/poorer bacterial clearance observed in males are due to increased lamin A levels. 3. Map relationships between lamin A-regulated nuclear architecture and wider male/female gene

expression changes. Altered lamin levels likely alter genome organisation/mechanosignal transduction to effect changes in gene expression. DamID will be done to compare male/female genome organisation in macrophage and muscle systems and integrated with our1,3 and others DamID, Hi-C, and RNA-Seq datasets on immune activation, myogenesis, and muscular dystrophy patients. Correlations between genome

organisation and expression differences affecting inflammatory pathways would further support lamin A levels as the driving force behind functional sex differences.