Institut du Fer à Moulin

Abstract Background and Aims The mechanisms driving the development of extracapillary lesions in crescentic glomerulonephritis (CGN) and focal segmental glomerulosclerosis (FSGS) remain poorly understood. This study investigates the role of serotonin (5-HT) and its receptors, specifically HTR2A and HTR2B, in murine models of these diseases. Method This study employed a combination of genetic, pharmacological, and in vitro approaches to elucidate the role of serotonin receptors in CGN and FSGS. Results We found that both receptors were upregulated in glomerular parietal epithelial cells in both human and murine CGN. We found that both genetic deletion and pharmacological inhibition of the 5-HT2A receptor effectively reduced glomerular crescents and sclerosis, while the compensatory upregulation of 5-HT2A receptors in response to 5-HT2B receptor deficiency or antagonism underscores a complex interplay between these receptor subtypes. Bone marrow-specific deletion and repletion of HTR2A-competent cells did not alter the course of experimental CGN, suggesting that the 2A signals driving CGN originate from the kidney. The Alport model, which is primarily degenerative, also benefitted in a similar way from 2A deletion, further corroborating the role of kidney resident 2A signaling in these diseases. Additionally, platelets were identified as a source of 5-HT and a crucial upstream factor in promoting PEC activation and exacerbating the disease, with their depletion leading to significant mitigation of disease severity. Finally, in vitro studies using murine PECs indicated the pivotal role of 5-HT signaling in PEC activation. Conclusion Our findings highlight a critical role of 5-HTR2A in PEC activation, proposing it as a new potential target for the treatment of glomerular kidney diseases.

ABSTRACT Around 3500 New Zealand women will be diagnosed with breast cancer each year. Of these, 45% will be diagnosed through mammography screening, either through BreastScreen Aotearoa or through the private sector. Those diagnosed through screening have better outcomes and importantly more equitable outcomes for Māori and Pacific women. With the advent of many technological changes, there are opportunities to increase the proportion of women who are diagnosed early through systematic screening and thus improve overall mortality from breast cancer. This article discusses the potential opportunities including widening the screening age and addressing the differences in screening rates for Māori and other ethnicities. The review also discusses potential changes to the screening modality (mammography), the value of grading breast density and the use of personalised screening. Finally, the article addresses the potential uses of Artificial Intelligence in assessing risk of cancer and in improving diagnostic accuracy of mammography.

The prefrontal cortex (PFC) plays a key role in high-level cognitive functions and emotional behaviors, and PFC alterations correlate with different brain disorders including major depression and anxiety. In mice, the first two postnatal weeks represent a critical period of high sensitivity to environmental changes. In this temporal window, serotonin (5-HT) levels regulate the wiring of PFC cortical neurons. Early-life insults and postnatal exposure to the selective serotonin reuptake inhibitor fluoxetine (FLX) affect PFC development leading to depressive and anxiety-like phenotypes in adult mice. However, the mechanisms responsible for these dysfunctions remain obscure. We found that early postnatal FLX exposure (PNFLX) results in reduced overall firing and high-frequency bursting of putative pyramidal neurons (PNs) of deep layers of the medial PFC of adult mice of both sexes in vivo. Ex vivo, patch-clamp recordings revealed that PNFLX abolished high-frequency firing in a distinct subpopulation of deep-layer mPFC PNs, which transiently express the serotonin transporter SERT during the first 2 postnatal weeks. SERT+ and SERT- PNs exhibit distinct morphofunctional properties. Genetic deletion of 5-HT7Rs and pharmacological 5-HT7R blockade partially rescued both the PNFLX-induced reduction of PN firing in vivo and the altered firing of SERT+ PNs in vitro. This indicates a pivotal role of this 5-HTR subtype in mediating 5-HT-dependent maturation of PFC circuits that are susceptible to early-life insults. Overall, our results suggest potential novel neurobiological mechanisms, underlying detrimental neurodevelopmental consequences induced by early-life alterations of 5-HT levels.

PurposeSince the COVID-19 pandemic, olfactory loss has been recognized as a highly prevalent condition that greatly impacts the quality of life. Similar to other sensory implants, the idea of an olfactory implant has emerged. Evidence indicates that electrical stimulation of specific olfactory structures can evoke smell sensations. However, debates on the most appropriate anatomical target and surgical technique for implantation are still ongoing. By extrapolating data from other surgical indications, transcranial approaches appear to carry a lower risk of cerebrospinal fluid leakage and infection compared with endoscopic endonasal routes. The aim of this study was to compare two electrode placements (dorsal olfactory bulb and ventral olfactory tract) through a supraorbital keyhole craniotomy in human cadavers.MethodFour fresh human cadavers were dissected in a staged manner. Supraorbital keyhole craniotomy was performed through an eyebrow incision and the frontal lobe was slightly retracted to allow angled (30°) endoscope insertion. An auditory brainstem implant (ABI) from MED-EL was used for electrode placement.ResultsEndoscopic placement of the electrode on the dorsal side of the olfactory bulb was achieved after orbital roof drilling in all cases, but was not stable. On the contrary, endoscopic placement of an electrode under the olfactory tract was easily achieved without drilling and the electrode was stable between the olfactory tract and the planum sphenoidale, behind the olfactory bulb.ConclusionVentral olfactory tract implantation posterior to the olfactory bulb using an ABI is straightforward and is associated with satisfactory electrode stability. Such a procedure could be used for clinical pilot studies evaluating the effects of various stimulation protocols on the olfactory tract in patients with long-lasting olfactory loss.

We investigated the impact of the human-specific gene CHRFAM7A on the function of α7 nicotinic acetylcholine receptors (α7 nAChRs) in two different types of neurons: human-induced pluripotent stem cell (hiPSC)-derived cortical neurons, and superior cervical ganglion (SCG) neurons, taken from transgenic mice expressing CHRFAM7A. dupα7, the gene product of CHRFAM7A, which lacks a major part of the extracellular N-terminal ligand-binding domain, co-assembles with α7, the gene product of CHRNA7. We assessed the receptor function in hiPSC-derived cortical and SCG neurons with Fura-2 calcium imaging and three different α7-specific ligands: PNU282987, choline, and 4BP-TQS. Given the short-lived open state of α7 receptors, we combined the two orthosteric agonists PNU282987 and choline with the type-2 positive allosteric modulator (PAM II) PNU120596. In line with different cellular models used previously, we demonstrate that CHRFAM7A has a major impact on nicotinic α7 nAChRs by reducing calcium transients in response to all three agonists.

Mutations of KIF7, a key ciliary component of Sonic Hedgehog (SHH) pathway, are associated in humans with cerebral cortex malformations and clinical features suggestive of cortical dysfunction. KIF7 regulates the processing of GLI-A and GLI3-R transcription factors in a SHH-dependent manner both in humans and in mice. Here, we examine the embryonic cortex development of a mouse model that lacks the expression of KIF7 (Kif7-/-). The cortex is composed of principal neurons generated locally in the dorsal telencephalon where SHH expression is low and inhibitory interneurons (cIN) generated in the ventral telencephalon where SHH expression is high. We observe a strong impact of Kif7 deletion on the dorsal cortex development whose abnormalities resemble those of GLI3-R mutants: subplate cells are absent, the intermediate progenitor layer and cortical plate do not segregate properly, and corticofugal axons do not develop timely, leading to a delayed colonization of the telencephalon by thalamocortical axons. These structural defects alter the cortical distribution of cIN, which moreover exhibit intrinsic migration defects and cortical trajectories resembling those of cyclopamine-treated cIN. Our results show that Kif7 deletion impairs the cortex development in multiple ways, exhibiting opposite effects on SHH pathway activity in the developing principal neurons and inhibitory interneurons.

Abstract Huntington’s disease (HD) is a devastating disease due to autosomal dominant mutation in theHTTgene. Its pathophysiology involves multiple molecular alterations including transcriptional defects. We previously showed that in HD patients and mouse model, the protein levels of the non-receptor tyrosine kinase PYK2 were decreased in the hippocampus and that viral expression of PYK2 improved the hippocampal phenotype. Here, we investigated the possible contribution of PYK2 in the striatum, a major brain region altered in HD. PYK2 mRNA levels were decreased in the striatum and hippocampus of R6/2 mice, a severe HD model. PYK2 protein levels were also decreased in the dorsal striatum of R6/2 mice and in the putamen of human patients. PYK2 knockout by itself did not result in motor symptoms observed in HD mouse models. Yet, we examined whether PYK2 deficiency participated in the R6/2 mice phenotype by expressing PYK2 in the dorsal striatum using AAV vectors. With an AAV1/Camk2apromoter, we did not observe significant improvement of body weight, clasping, motor activity and coordination (rotarod) alterations observed in R6/2 mice. With an AAV9/SYN1promoter we found an improvement of body weight loss and a tendency to better rotarod performance. DARPP-32 immunofluorescence was increased following AAV9/SYN1-PYK2 injection compared to AAV9/SYN1-GFP, suggesting a possible partial beneficial effect on striatal projection neurons. We conclude that PYK2 mRNA and protein levels are decreased in the striatum as in hippocampus of HD patients and mouse models. However, in contrast to hippocampus, striatal viral expression of PYK2 has only a slight effect on the R6/2 model striatal motor phenotype.HighlightsHuntington’s disease is a lethal genetic disease altering striatum, cortex, and hippocampusRestoring PYK2 levels in hippocampus improved hippocampal phenotype of a Huntington mouse modelWe show that PYK2 levels are decreased in the striatum of R6/2 mice and human patientsViral expression of PYK2 in the striatum has only a small effect on R6/2 mouse model motor phenotype but improves weight loss

SummaryThe prefrontal cortex (PFC) plays a key role in high-level cognitive functions and emotional behaviors, and PFC alterations correlate with different brain disorders including major depression and anxiety. In mice, the first two postnatal weeks represent a critical period of high sensitivity to environmental changes. In this temporal window, serotonin (5- HT) levels regulate the wiring of PFC cortical neurons. Early life insults and postnatal exposure to the selective serotonin reuptake inhibitor fluoxetine (FLX) affect PFC development leading to depressive and anxiety-like phenotypes in adult mice. However, the mechanisms responsible for these dysfunctions remain obscure. We found that postnatal FLX exposure (PNFLX) results in reduced overall firing, and high-frequency bursting of putative pyramidal neurons (PNs) of deep layers of the medial PFC (mPFC) of adult mice in vivo. Ex-vivo, patch-clamp recordings revealed that PNFLX abolished high-frequency firing in a distinct subpopulation of deep-layer mPFC PNs, which transiently express the serotonin transporter SERT. SERT+ and SERT- PNs exhibit distinct morpho-functional properties. Genetic deletion of 5-HT7Rs prevented the PNFLX-induced reduction of PN firingin vivoand pharmacological 5-HT7R blockade precluded altered firing of SERT+ PNsin vitro. This indicates a pivotal role of this 5-HTR subtype in mediating 5-HT-dependent maturation of PFC circuits that are susceptible to early-life insults. Overall, our results suggest potential novel neurobiological mechanisms, underlying detrimental neurodevelopmental consequences induced by early-life alterations of 5-HT levels.

Grey matter heterotopia (GMH) are neurodevelopmental disorders associated with abnormal cortical function and epilepsy. Subcortical band heterotopia (SBH) and periventricular nodular heterotopia (PVNH) are two well-recognized GMH subtypes in which neurons are misplaced, either forming nodules lining the ventricles in PVNH, or forming bands in the white matter in SBH. Although both PVNH and SBH are commonly associated with epilepsy, it is unclear whether these two GMH subtypes differ in terms of pathological consequences or, on the contrary, share common altered mechanisms. Here, we studied two robust preclinical models of SBH and PVNH, and performed a systematic comparative assessment of the physiological and morphological diversity of heterotopia neurons, as well as the dynamics of epileptiform activity and input connectivity. We uncovered a complex set of altered properties, including both common and distinct physiological and morphological features across heterotopia subtypes, and associated with specific dynamics of epileptiform activity. Taken together, these results suggest that pro-epileptic circuits in GMH are, at least in part, composed of neurons with distinct, subtype-specific, physiological and morphological properties depending on the heterotopia subtype. Our work supports the notion that GMH represent a complex set of disorders, associating both shared and diverging pathological consequences, and contributing to forming epileptogenic networks with specific properties. A deeper understanding of these properties may help to refine current GMH classification schemes by identifying morpho-electric signatures of GMH subtypes, to potentially inform new treatment strategies.