Biology subjects

Picard, N.

Publications and source records attributed to Picard, N..

6 recordsLinked to original sources

bioRxiv2026

Renal adaptation to high salt diet requires tubular Na+ secretion through type A intercalated cells

BackgroundIn the context of increased salt intake in the world population, the understanding of the mechanisms that contribute to its correct renal excretion and therefore, avoid variation of blood volume and blood pressure is of major importance. MethodsMolecular, ex vivo microperfusion on isolated tubules, and integrative analysis, was used to identify, characterize and investigate a Na+ secretion pathway in the collecting duct. ResultsIn collecting duct of mice, salt load induced an increase of the type A intercalated cells (AIC) number, an overexpression of the H(Na),K-ATPase type 2 (HKA2) catalytic subunit Atp12a and a stimulation of the bumetanide-sensitive Na+ secretion in isolated and microperfused tubules. Surprisingly, HKA2KO mice fed a high-salt diet exhibit a strong dysregulation of their Na+ and water balance with a pronounced loss of Na+ and fluid, alkalosis, hypokalemia and low blood pressure. This Bartter-like phenotype is due to an over-inhibition of the thick ascending limb (TAL) related to an elevated PGE2 production. ConclusionOur findings establish that activation of Na+ secretion in AIC act as the fine-tuning knob in the regulation of renal Na+ excretion in response to high salt intake. Its absence is overcompensated by an inhibition of the Na+ transport system of the TAL.

physiology↗

bioRxiv2024

Gradual consolidation of skilled sequential movements in primary motor cortex of non-human primates

Many of our daily actions rely on skilled sequential movements. Sequence performance improves with practice and can reach expert levels with years of repeated practice, truly exemplifying the saying "Practice makes perfect". Human and non-human primate studies have shown structural and functional changes in the primary motor cortex (M1) following extended practice of sequential movements, suggesting M1s involvement in acquisition and retention of skilled sequential movements. However, it has been challenging to causally examine M1s role in sequence learning, because inactivation or lesion of M1 impairs movement production itself. Here, we causally examined M1s contribution to learning of sequential movements by locally inhibiting protein synthesis in M1. Our results show that protein synthesis inhibition in M1 disrupted memory-guided sequential movements at all stages of learning without affecting visually guided reaching, though the effects decreased with continued practice. These findings suggest that neural representations of sequential movements are repeatedly consolidated in M1 through protein synthesis, with the rate of consolidation slowing as learning progresses. TeaserRepetitive practice strengthens neural representations of sequential movements in primary motor cortex of monkeys.

neuroscience↗

bioRxiv2024

Renal proximal tubules are sensitive to metabolic acidosis

Patients suffering from distal renal tubular acidosis (dRTA) are sometimes diagnosed with proximal tubule dysfunction with leaks of phosphate, uric acid, amino acids, and low-molecular-weight proteins, also known as Fanconi-like syndrome. The underlying molecular basis is largely elusive. We previously reported on Atp6v0a4 knockout (KO) mice, which exhibit severe metabolic acidosis in combination with proximal tubule dysfunction as evidenced by phosphaturia and proteinuria. Here, we show that Rab7, a key regulator of endo-lysosomal trafficking and lysosomal biogenesis, is strongly diminished in proximal tubules of Atp6v0a4 KO mice, while the number of abnormal Ist1-labelled Lamp1-positive vesicles is increased. This is accompanied by the accumulation of autophagosomes, autolysosomes and autophagic substrates. Importantly, correction of metabolic acidosis with bicarbonate therapy resolves proximal tubule dysfunction and trafficking defects in Atp6v0a4 KO mice. Acid-challenged wildtype mice also show trafficking defects with Rab7-downregulation and an increase in Ist1-labeled Lamp1-positive vesicles and develop proximal tubule damage in the long-term. Similar acidosis-induced alterations also occur in human kidney organoids. Altogether, our data provide insights, why patients suffering from severe dRTA may develop a Fanconi-like syndrome, which may contribute to the progression of chronic kidney failure. Translational StatementPatients with renal acidosis caused by impaired proton secretion in the collecting duct (distal renal tubular acidosis - dRTA) sometimes show unexplained symptoms of proximal tubule dysfunction such as proteinuria and phosphaturia. Here, we show that proximal tubules are particularly sensitive to acidosis as evidenced by impaired trafficking, lysosomal damage and accumulation of autophagic substrates. We also show that early treatment of dRTA by alkali supplementation can prevent proximal tubule dysfunction. Because metabolic acidosis represents a well-known risk factor for the progression of chronic kidney disease (CKD), our findings highlight the potential clinical importance of early alkali supplementation to delay disease progression.

molecular biology↗

bioRxiv2022

GDF15 mediates renal cell plasticity in response to potassium depletion

A low potassium (K+) intake is a common situation in the population of the Westernized countries where processed food is prevalent in the diet. Here, we show that expression of GDF15, a TGF{beta}-related growth factor, is increased in renal tubular segments and gut parts of mice in response to low-K+ diet leading to a systemic elevation of its plasma and urine concentration. In human, under mild dietary K+ restriction, we observed that urine GDF15 excretion is correlated with plasma K+ level. Conversely to WT mice, adaptation to K+ restriction of GDF15-KO mice is not optimal, they do not increase their number of type A intercalated cell, responsible for K+ retention, and have a delayed renal K+ retention, leading to early development of hypokalemia. This renal effect of GDF15 depends on ErBb2 receptor, whose expression is increased in the kidney collecting ducts. We also observe that, in the absence of GDF15, the release of K+ by the muscles is blunted which is compensated by a loss of muscle mass. Thus, in this study, we showed that GDF15 plays a central role in the response to K+ restriction by orchestrating the modification of the cell composition of the collecting duct.

physiology↗

bioRxiv2022

Differentiated neuroblastoma cells remain epigenetically poised for de-differentiation to an immature state

Neuroblastoma is the most common extracranial solid tumor of childhood and accounts for a significant share of childhood cancer deaths. Prior studies utilizing RNA sequencing of bulk tumor populations showed two predominant cell states characterized by high and low expression of neuronal genes. Although cells respond to treatment by altering their gene expression, it is unclear whether this reflects shifting balances of distinct subpopulations or plasticity of individual cells. Using neuroblastoma cell lines lacking MYCN amplification, we show that the antigen CD49b distinguishes these subpopulations. CD49b expression marks proliferative cells with an immature gene expression program, while CD49b-negative cells express differentiated neuronal marker genes and are quiescent. Sorted populations spontaneously switch between CD49b expression states in culture, and CD49b-negative cells can generate rapidly growing, CD49b-positive tumors in mice. We profiled H3K27ac to identify enhancers and super enhancers that are specifically active in each population and find that CD49b-negative cells maintain the priming H3K4me1 mark at elements that are active in CD49b-high cells. Improper maintenance of primed enhancer elements thus may underlie cellular plasticity in neuroblastoma, representing potential therapeutic targets for this lethal tumor. Summary StatementThis study demonstrates that neuroblastoma cells can interconvert between a state characterized by expression of neuronal genes and a de-differentiated state.

cancer biology↗

bioRxiv2018

Distribution maps of twenty-four Mediterranean and European ecologically and economically important forest tree species compiled from historical data collections

Background Background Methods Access to data and... Technical validation Reuse potential and limits Contribution of the co-authors Funding References Information on species geographic distribution is a strategic scientific resource for many research, innovation and development purposes, such as: biodiversity assessment, habitat and species management, restoration and conservation as well as for predicting the effects of global environmental change on ecosystems, species and populations and their genetic resources (Fady et al. 2016; Franklin 2009; Noce et al. 2016; Sinclair et al. 2010).\n\nMaps are one of the ways information on geographic distribution can best be summarized and used ( ...

ecology↗