Wright, B. R. | Search bioRxiv

bioRxiv2025

Paediatric MRI: High-Resolution in vivo 3T Methods

Magnetic Resonance Imaging (MRI) is a powerful tool for investigating the brain in vivo but is limited by image resolution and scan artefact. In paediatric research, these limitations are compounded by reduced participant compliance, which in turn necessitates shorter scan times to minimise motion artefacts, resulting in less than satisfactory image resolution. We report here methods for MRI acquisition which afford high-resolution, low-noise, paediatric brain data in under nine-minute scans, and novel post-processing with our code freely available at https://osf.io/ckh5t/. Whole-brain in vivo single-participant images were generated at 0.5mm isotropic resolution. This resolution permitted accurate delineation of fine structures, including the hippocampal subfields. The ability to resolve intricate structures in paediatric data provides a tool for studying brain development and its disruption in neurologic and psychiatric disorders.

neuroscience↗

bioRxiv2025

Inbreeding and resultant homozygosity across key inflammation and DNA repair genes linked to chlamydial infection in New South Wales koalas

Inbreeding and resultant homozygosity can reduce genetic diversity and increase disease susceptibility. Koalas (Phascolarctos cinereus) are one species suffering genomic diversity loss and inbreeding and concurrent significant disease pressure (particularly chlamydiosis). Using 259 whole genomes with a pathogen sampling regime we identify potential links between inbreeding, genome-wide variation and chlamydial infection. We found a general trend of reduced genomic diversity and increased inbreeding from north to south across six sites in New South Wales. A genome-wide association study of 153 individuals from sites with known Chlamydia pecorum presence were used to investigate the potential relationship between inbreeding and infection. Chlamydia positive individuals (average FH = 0.026) were significantly more inbred than Chlamydia negative individuals (average FH= -0.0051) (t = - 2.31, df = 151, p-value = 0.022). We identified several genes involved in host-pathogen interactions and DNA mismatch repair within in runs of homozygosity that were unique to Chlamydia positive individuals. Interestingly, populations considered putatively Chlamydia-free had similar allele frequencies across candidate loci as Chlamydia positive individuals. Combined with gene flow analyses, this result suggests that isolation may have protected these populations more than harbouring alleles conferring infection resilience and supports the concept that disease should be carefully considered in any conservation measures that increase connectivity or translocations. Our genome-wide approach has identified several avenues for investigations into the pathogenesis of Chlamydia infection and chlamydiosis. We showcase the value of high-quality re-sequenced genomes for understanding the implications of inbreeding, genomic diversity loss, and infection susceptibility, all universal problems for threatened species.

genomics↗