Biology subjects

Finnemann, S. C.

Publications and source records attributed to Finnemann, S. C..

3 recordsLinked to original sources

bioRxiv2022

Inflammation Of The Retinal Pigment Epithelium Drives Early-Onset Photoreceptor Degeneration In Mertk-Associated Retinitis Pigmentosa

Severe, early-onset photoreceptor (PR) degeneration associated with MERTK mutations is thought to result from failed phagocytosis by retinal pigment epithelium (RPE). Notwithstanding, the severity and onset of PR degeneration in mouse models of Mertk ablation is determined by the hypomorphic expression or the loss of the Mertk paralog Tyro3. Here we find that loss of Mertk and reduced expression/loss of Tyro3 led to RPE inflammation even before eye-opening. Incipient RPE inflammation cascaded to involve microglia activation and PR degeneration with monocyte infiltration. Inhibition of RPE inflammation with the JAK1/2 inhibitor ruxolitinib mitigated PR degeneration in Mertk-/- mice. Neither inflammation nor severe, early-onset PR degeneration were observed in mice with defective phagocytosis alone. Thus, inflammation drives severe, early-onset PR degeneration-associated with Mertk loss of function.

immunology↗

bioRxiv2022

Tissue-specific modifier alleles determine Mertk loss-of-function traits

Knockout (KO) mouse models play critical roles in elucidating biological processes behind disease-associated or disease-resistant traits. As a consequence of gene KO, mice display certain phenotypes. Based on insight into the molecular role of said gene in a biological process, it is inferred that the particular biological process causally underlies the trait. This approach has been crucial towards understanding the basis of pathological and/or advantageous traits associated with Mertk KO. MERTK is a receptor tyrosine kinase with a critical role in phagocytosis of apoptotic cells or cellular debris. Therefore, early-onset, severe retinal degeneration was described to be a direct consequence of failed phagocytosis of photoreceptor outer segments by retinal pigment epithelia. Similarly, enhanced anti-tumor immunity was inferred to result from the failure of macrophages to dispose cancer cell corpses, resulting in a pro-inflammatory tumor microenvironment. Here we report that the loss of Mertk alone is not sufficient for retinal degeneration. This trait only manifests when the function of the paralog Tyro3 is concomitantly lost. Additionally, the dramatic resistance against two syngeneic mouse tumor models observed in Mertk KO cannot, at least entirely, be ascribed to the loss of Mertk. The widely used Mertk KO carries multiple coincidental changes in its genome that affect the expression of a number of genes, including Tyro3. Nonetheless, neither Tyro3, nor macrophage phagocytosis by alternate genetic redundancy, accounts for the absence of anti-tumor immunity in two independent Mertk KOs. Collectively, our results indicate that context-dependent epistasis of independent modifier alleles determine Mertk KO traits.

immunology↗

bioRxiv2021

Sex-specific multi-level 3D genome dynamics in the mouse brain

The female mammalian brain exhibits sex-hormone-driven plasticity during the reproductive period. Evidence implicates chromatin dynamics in gene regulation underlying this plasticity. However, whether ovarian hormones impact higher-order chromatin organization in post-mitotic neurons in vivo is unknown. Here, we mapped 3D genome of ventral hippocampal neurons across the estrous cycle and by sex in mice. In females, we found cycle-driven dynamism in 3D chromatin organization, including in estrogen-response-elements-enriched X-chromosome compartments, autosomal CTCF loops, and enhancer-promoter interactions. With rising estrogen levels, the female 3D genome becomes more similar to the male genome. Cyclical enhancer-promoter interactions are partially associated with gene expression and enriched for brain disorder-relevant genes. Our study reveals unique 3D genome dynamics in the female brain relevant to female-specific gene regulation, neuroplasticity, and disease risk.

neuroscience↗