Programmed axon death is a widespread and completely preventable mechanism in injury and disease. Mouse and Drosophila studies define a molecular pathway involving activation of SARM1 NA Dase and its prevention by NAD synthesising enzyme NMNAT2 . Loss of axonal NMNAT2 causes its substrate, NMN , to accumulate and activate SARM1 , driving loss of NAD and changes in ATP , ROS and calcium. Animal models caused by genetic mutation, toxins, viruses or metabolic defects can be alleviated by blocking programmed axon death, for example models of CMT1B , chemotherapy-induced peripheral neuropathy (CIPN), rabies and diabetic peripheral neuropathy (DPN). The perinatal lethality of NMNAT2 null mice is completely rescued, restoring a normal, healthy lifespan. Animal models lack the genetic and environmental diversity present in human populations and this is problematic for modelling gene-environment combinations, for example in CIPN and DPN , and identifying rare, pathogenic mutations. Instead, by testing human gene variants in WGS datasets for loss- and gain-of-function, we identified enrichment of rare SARM1 gain-of-function variants in sporadic ALS , despite previous negative findings in SOD1 transgenic mice. We have shown in mice that heterozygous SARM1 loss-of-function is protective from a range of axonal stresses and that naturally-occurring SARM1 loss-of-function alleles are present in human populations. This enables new approaches to identify disorders where blocking SARM1 may be therapeutically useful, and the existence of two dominant negative human variants in healthy adults is some of the best evidence available that drugs blocking SARM1 are likely to be safe. Further loss- and gain-of-function variants in SARM1 and NMNAT2 are being identified and used to extend and strengthen the evidence of association with neurological disorders. We aim to identify diseases, and specific patients, in whom SARM1 -blocking drugs are most likely to be effective.

Genome-wide association studies and functional genomics studies have linked specific cell types, genes, and pathways to Alzheimer’s disease (AD) risk. In particular, AD risk alleles primarily affect the abundance or structure, and thus the activity, of genes expressed in macrophages, strongly implicating microglia (the brain-resident macrophages) in the etiology of AD. These genes converge on pathways (endocytosis/phagocytosis, cholesterol metabolism, and immune response) with critical roles in core macrophage functions such as efferocytosis. Here, we review these pathways, highlighting relevant genes identified in the latest AD genetics and genomics studies, and describe how they may contribute to AD pathogenesis. Investigating the functional impact of AD-associated variants and genes in microglia is essential for elucidating disease risk mechanisms and developing effective therapeutic approaches." https://doi.org/10.1016/j.neuron.2022.10.015

SCN8A encodes a major voltage-gated sodium channel expressed in CNS and PNS neurons.  Gain-of-function and loss-of-function mutations contribute to  human disorders, most notably Developmental and Epileptic Encephalophy (DEE). More than 600 affected individuals have been reported, with the most common  mechanism of de novo, gain-of-function mutations.  We have developed constitutive  and conditional models of gain- and loss- of function mutations in the mouse and  characterized the effects of on neuronal firing and neurological phenotypes.  Using CRE lines with cellular and developmental specificity, we have probed the effects of activating  mutant alleles in various classes of neurons in the developing and adult mouse.   Most recently, we are testing genetic therapies that reduce the expression  of gain-of-function mutant alleles.  We are comparing the effectiveness of allele specific  oligos (ASOs), viral delivery of shRNAs, and allele-specific targeting of mutant alleles  using Crispr/Cas9 in mouse models of DEE.

Natural selection affects not only selected alleles, but also indirectly affects all genes near selected sites on the genome. An increasing body of evidence suggests that this linked selection is an important driver of evolutionary dynamics throughout the genomes of many species, implying that we need to substantially revise our basic understanding of molecular evolution. This session brings together early-career researchers working towards a quantitative understanding of the prevalence and effects of linked selection.