Kolli, V. | bioRxiv Science

bioRxiv2025

A Novel Patient-Derived Mutation in Glucocorticoid Receptor Reveals an Essential Role for DNA binding in Development and Endocrine Regulation

Glucocorticoid receptors (GRs) are vital transcription factors regulating stress responses, metabolism, and development. We report here a novel heterozygous NR3C1 c.1310C>T (p.T437I) variant within the GR DNA-binding domain found in a family exhibiting clinical and hormonal manifestations of partial glucocorticoid resistance. Patient-derived fibroblasts demonstrated an overall suppression in dexamethasone-induced transcription. To comprehensively assess the significance of the variant, we engineered a knock-in mouse model (Nr3c1+/T444I mice) using CRISPR-Cas9, providing an in vivo model of the patient-derived GR mutation at the orthologous residue. Heterozygous mice exhibited partial glucocorticoid resistance, dysregulated HPA axis activity and impaired dexamethasone suppression, closely recapitulating the patient phenotype. Homozygous Nr3c1T444I/T444I embryos were recovered at embryonic day 12.5 (E12.5) but did not survive to term, indicating mid-gestational lethality. Transcriptomic profiling of primary mouse embryonic fibroblasts revealed dosage-dependent effects with heterozygotes showing an intermediate response to dexamethasone compared to wild-type, while homozygotes showed a markedly blunted response. Our results challenge prior assumptions by demonstrating that GR DNA-binding is essential for embryogenesis, while offering a new preclinical platform to investigate glucocorticoid resistance pathophysiology and therapeutic interventions.

genetics↗

bioRxiv2023

Does ipsilateral remapping following hand loss impact motor control of the intact hand?

What happens once a cortical territory becomes functionally redundant? We addressed brain and behavioural adaptations for the intact hand in individuals with a missing hand. Previous studies reported increased ipsilateral activity in the somatosensory territory of the missing hand (i.e., remapping) in acquired amputees, but not in individuals with a congenitally missing hand (one-handers). It is unclear whether remapping in amputees involves recruiting more neural resources to support the intact hand, and whether such activity is increased in tasks that demand greater motor control. We investigated sensorimotor learning and neural representation of the intact hand in one-handers and amputees using a multi-finger configuration task, as well as univariate and multivariate fMRI. We found that ipsilateral activity increased with motor demand - but only in the amputees group. However, these changes did not reflect behavioural differences. The representation of the finger configurations, as revealed by multivariate analysis, was stronger in amputees and closer to the typical representation found in controls contralateral hand territory, compared to one-handers. This collaborative contra-ipsilateral activity may reflect the intact hands efference copy. One-handers struggled to learn difficult finger configurations, but this did not translate to differences in univariate or multivariate activity relative to controls. Together with a supplementary structural white matter analysis, our results suggest that enhanced activity in the missing hand territory may not reflect intact hand function. Instead, we suggest that plasticity is more restricted than generally assumed and may depend on the availability of homologous pathways acquired early in life. Significant StatementWe studied whether brain resources in the missing-hand territory support demanding intact hand motor control in people who were born with one hand or lost a hand later in life. We found that amputees had increased activity in the brain area used for the missing hand, but no improvement in the performance of their intact hand. This collaborative contra-ipsilateral activity may reflect the intact hands efference copy. One-handers showed slight deficits while learning to perform complex motor movements, but no brain activity differences in the missing hand territory, compared to controls. Our results suggest that brain plasticity is limited and may depend on early life experiences.

neuroscience↗