Biology subjects

Ranpura, G.

Publications and source records attributed to Ranpura, G..

5 recordsLinked to original sources

bioRxiv2025

A conserved distal element in the mouse Csf1r locus contributes to transcription in hematopoietic and trophoblast cells.

Expression of the Csf1r gene in mice is restricted to cells of the mononuclear phagocyte system and placental trophoblasts. A conserved element (Csf1r upstream regulatory element A, CUREA) in the mouse Csf1r locus contains transcription start sites utilised by trophoblasts and osteoclasts and an enhancer essential for expression of multicopy transgenic reporters in most tissue macrophages. Here we describe the impact of deletion of CUREA in the mouse genome, on the background of a knock-in Csf1r-FusionRed reporter. By contrast to the essential function in transgene expression, CUREA deletion had no effect on expression of FusionRed or differentiation of blood monocytes or tissue resident macrophages. The deletion reduced Csf1r mRNA in hematopoietic stem cells and committed myeloid progenitors (MPP3) leading to a subtle differentiation delay and also had a significant impact on microglial phenotype in the brain and the differentiation of osteoclasts. The expression of FusionRed in placenta confirmed expression of CSF1R in trophoblasts. 5RACE analysis demonstrated that the effect of CUREA deletion on Csf1r transcription in placenta was overcome by the use of cryptic upstream transcription start sites. We conclude that CUREA is a regulatory element controlling Csf1r transcription. The function overlaps with other enhancers identified in the locus and is therefore partly redundant. Key PointsO_LIA regulatory element (CUREA) in the mouse Csf1r locus has both promoter and enhancer activity. C_LIO_LIGerm-line deletion of CUREA impacts differentiation of marrow progenitors, microglia, osteoclasts and placental trophoblasts. C_LI

cell biology↗

bioRxiv2025

Homozygous kinase-dead Csf1r mutation in outbred mice reveals essential and redundant functions of tissue resident macrophages

The proliferation, differentiation and survival of cells of the macrophage lineage depends on signals from the macrophage colony-stimulating factor receptor (CSF1R). On a C57BL/6J background homozygous kinase-dead Csf1r mutation (Csf1rE631K/E631K - E631Km/m) causes perinatal lethality. Here we demonstrate that E631Km/m mice on a mixed genetic background (C57 x BALB/c F2) are osteopetrotic and growth retarded but viable as adults with no other gross developmental deficits. They lack osteoclasts, microglia and most peripheral tissue resident macrophages and exhibit perturbed hematopoiesis. Although CD169+ tissue resident macrophages in bone marrow are considered an essential component of the hematopoietic niche, CD169 is undetectable in E631Km/m marrow and F4/80+ macrophages are depleted. These changes are associated with expansion of mature and immature granulocytes and reduced B cells, whereas monocytes and stem and progenitor populations are unaffected as a proportion of total cells. Erythropoiesis in bone marrow is maintained in E631Km/m mice, associated with a residual population of CSF1R-independent CD169-ve/F4/80+ macrophages. Nevertheless, splenic extramedullary hematopoiesis in E631Km/m mice indicates a degree of bone marrow insufficiency. Red pulp macrophages are retained but CD169+ marginal metallophil macrophages are absent and CD209b+ (SIGNR1) macrophages are present but disorganized. Circulating white blood cell count is unchanged in E631Km/m mice, but the proportion of neutrophils is greatly increased whilst B cells and monocytes are reduced. This novel model reveals the essential roles of CSF1R-dependent macrophages in hematopoiesis and demonstrates that many developmental and homeostatic functions attributed to murine resident tissue macrophages are redundant and/or specific to inbred mouse strains.

immunology↗

bioRxiv2025

Mutation in the rat interleukin 34 gene impacts macrophage development, homeostasis and inflammation in the brain and periphery

Interleukin-34 (IL34) and colony stimulating factor 1 (CSF1) signal through a shared receptor (CSF1R) to control macrophage survival, differentiation and function. Here we describe the impact of loss of function mutation in the rat Il34 gene. Il34-/- rats showed a partial reduction in macrophages within squamous epithelia (Langerhans-like cells) and in the testis. In the brain, microglia and brain-associated macrophages were selectively depleted in grey matter. A gradient of microglial density in Il34-/- cortex suggests that CSF1 can diffuse outwards from the corpus callosum. The reduced density of microglia was not associated with detectable neuropathology or behavioural alterations. In RNA-seq analysis of cortex, hippocampus and thalamus the only change is selective and uniform loss of the microglial signature. In the periphery, increased Il34 expression has been associated with epithelial injury. In the adenine diet model of renal interstitial fibrosis both Il34 and Csf1 were induced. The absence of IL34 led to a significant reduction in macrophage recruitment compared to controls, but pathology assessed histologically or by detection of damage-associated mRNA signature was unaffected. We suggest that IL34 and CSF1 provide redundant signals to sustain microglia and to direct macrophage recruitment and repair tissue injury in the periphery.

immunology↗

bioRxiv2025

Repopulation of the brain with microglia-like cells following intraperitoneal bone marrow cell transfer in microglia-deficient mice.

Germ-line deletion of a conserved enhancer (the Fms intrinsic regulatory element, FIRE) in the mouse Csf1r locus causes congenital absence of microglia. Homozygous FIRE deletion on a C57BL/6J background leads to perinatal lethality and hydrocephalus (HC) in surviving pups. We developed a congenic C57BL/6J line with defined regions of non-C57BL/6J genomic DNA, increased postnatal viability and reduced incidence of HC. Both perinatal lethality and HC were eliminated in F2 mice following outcross of the congenic line to CBA/J or BALBc/J backgrounds. To assess the impacts of microglial deficiency in postnatal neurodevelopment we analyzed deep total RNA-seq data from multiple brain regions of wild-type and Csf1r{Delta}FIRE/{Delta}FIRE mice. Aside from the loss of microglial-specific transcripts, we found no significant alterations in relative abundance of any cell-type or region-specific transcriptomic signature. Transcripts associated with endosome/lysosome function, which are enriched in microglia, were not affected, suggesting compensatory expression by other cell types. On the C57BL/6J x CBA/J F2 background, congenital absence of microglia did not affect motor activity, behavior or myelination up to 7 months of age but was associated with astrocytosis and calcification in the thalamus. In the congenic C57BL/6J Csf1r{Delta}FIRE/{Delta}FIRE mouse line, intraperitoneal transfer of wild-type bone marrow cells (BMT) at weaning led to complete repopulation of the brain with microglia-like cells without giving rise to monocytic intermediates. Our results suggest novel strategies for treatment of microglial deficiency.

neuroscience↗

bioRxiv2023

Slow conduction and spatial dispersion of repolarization are intrinsic properties of cardiomyocyte electrophysiology that contribute to proarrhythmia in an iPSC model of hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is an inherited heart muscle disease; characterised by left ventricular wall thickening, cardiomyocyte disarray, and fibrosis, and is associated with arrhythmias, heart failure and sudden death. However, it is unclear to what extent the electrophysiological disturbances that lead to sudden death occur secondary to the structural changes in the myocardium, or as a result of intrinsic properties of the HCM cardiomyocyte. In this study, we used an induced pluripotent stem cell model of the Arg403Gln variant in myosin heavy chain 7 (MYH7) to study tissue level electrophysiological properties of HCM cardiomyocytes. For the first time, we show significant slowing of conduction velocity and an increase in local spatial dispersion of repolarisation - both well-established substrates for arrhythmia - in monolayers of HCM cardiomyocytes. Analysis of rhythmonome protein expression in R403Q cardiomyocytes revealed dramatically reduced connexin-43, sodium channels, and inward rectifier channels - a three-way hit that combines to reduce electrotonic coupling between HCM cardiomyocytes and slow cardiac conduction. Our data therefore represent a novel, biophysical basis for arrhythmia in HCM, that is intrinsic to cardiomyocyte electrophysiology. Later in the progression of the disease, these proarrhythmic electrical phenotypes may be accentuated by fibrosis and myocyte disarray to contribute to sudden death in HCM patients.

physiology↗