Biology subjects

Sirchia, F.

Publications and source records attributed to Sirchia, F..

3 recordsLinked to original sources

bioRxiv2026

Disruption of endothelial stability directly impacts vascular neighboring cells in Hereditary Hemorrhagic Telangiectasia

BACKGROUNDHereditary hemorrhagic telangiectasia (HHT) is a genetic disorder caused by pathogenic variants in the endothelial TGF{beta}/BMP pathway, crucial for the vascular arterial-venous differentiation. Vascular defects result in fragile and malformed vessels. The precise mechanisms driving vascular network failure remain incompletely understood, complicating the design of targeted therapies. METHODSNasal telangiectasias from HHT patients carrying variants in ACVRL1 or ENG were used to perform scRNA-seq (2 ACVRL1- and 1 ENG-patient) and spatial transcriptomics (1 ACVRL1 and 1 ENG) to uncover endothelial cells (EC) populations. Vascular characteristics within biopsies were evaluated using transmission electron microscopy (TEM) (1 ACVRL1 and 1 ENG) and histological analyses (23 ACVRL1 and 7 ENG), with particular attention to regions exhibiting varying degrees of damage. RESULTSComparing our HHT tissues with healthy donor from the literature, we identified cellular heterogeneity within EC populations, revealing two distinct venous clusters: a stable, quiescent population (Mature Vein) and an activated, pro-inflammatory population (HHT Vein). The coexistence of these two clusters suggests cellular diversity within the biopsy, further validated by TEM and histology, revealing a juxtaposition of well-organized collagen and cellular architecture with severely disrupted, fibrotic regions. Moreover, cellular crosstalk analyses allowed us to identify critical ligands in ECs that interact with fibroblasts and mural cells. In particular, we found Midkine (MDK) lost in HHT Vein ECs with further validation in vitro, suggesting its potential role in cellular stability. Furthermore, spatial transcriptomics allowed to further uncover pathologic phenotypes in cells neighboring HHT Vein ECs. CONCLUSIONSHHT biopsies exhibit localized inflamed and fibrotic vascular areas with the presence of different transcriptional sub-populations of EC. Within the same tissue, stable and activated ECs can be distinguished. The pathologic-like EC cluster, present exclusively in the HHT samples, may contribute to vascular leakage through the loss of important ligands involved in cellular communication.

cell biology↗

bioRxiv2026

Comprehensive classification of HCN1 variants linked to neurodevelopmental disorders with and without epilepsy

Hyperpolarization-activated cyclic nucleotide-gated 1 channels (HCN1) mediate the Ih cationic current and play a central role in regulating neuronal excitability and synaptic integration. HCN1 is predominantly expressed in the neocortex and hippocampus. Pathogenic variants in HCN1 have been increasingly identified in individuals presenting with a broad spectrum of epileptic disorders, ranging from severe developmental and epileptic encephalopathy (DEE) to milder epilepsies. Here, we used patch-clamp electrophysiology in combination with confocal imaging in HEK293 cells to functionally characterize 43 HCN1 variants found in patients presenting with neurodevelopmental disorders, with or without epilepsy. Based on their biophysical properties, we defined four functional classes: (I) low or no current, (II) hyperpolarizing (i.e. left) shift in voltage dependence, (III) depolarizing (i.e. right) shift in voltage dependence, and (IV) generation of an instantaneous current. Integration of this functional classification with detailed clinical data from a cohort of 49 patients revealed a striking genotype-phenotype correlation. Loss-of-function variants were strongly enriched among individuals without epilepsy or with milder generalized phenotypes, whereas gain-of-function and mixed variants were predominantly associated with epilepsy, including all cases of DEE. Notably, non-epileptic cases clustered within a subgroup of loss-of-function variants affecting the selectivity filter. We further show that allosteric modulators, including the peptides NB6 and TRIP8bnano and the small molecule J&J12e, normalize the functional properties of mutant HCN1 channels in three classes. These findings establish a clinically relevant framework for interpreting HCN1 gain- and loss-of-function variants suggesting that the direction of channel dysfunction is a major determinant of epilepsy risk and severity.

pathology↗

bioRxiv2019

Variants in the degron of AFF3 cause a multi-system disorder with mesomelic dysplasia, horseshoe kidney and developmental and epileptic encephalopathy

The ALF transcription factor paralogs, AFF1, AFF2, AFF3 and AFF4, are components of the transcriptional super elongation complex that regulates expression of genes involved in neurogenesis and development. We describe a new autosomal dominant disorder associated with de novo missense variants in the degron of AFF3, a nine amino acid sequence important for its degradation. Consistent with a causative role of AFF3 variants, the mutated AFF3 proteins show reduced clearance. Ten affected individuals were identified, and present with a recognizable pattern of anomalies, which we named KINSSHIP syndrome (KI for horseshoe KIdney, NS for Nievergelt/Savarirayan type of mesomelic dysplasia, S for Seizures, H for Hypertrichosis, I for Intellectual disability and P for Pulmonary involvement), partially overlapping the AFF4 associated CHOPS syndrome. An eleventh individual with a microdeletion encompassing only the transactivation domain and degron motif of AFF3 exhibited overlapping clinical features. A zebrafish overexpression model that shows body axis anomalies provides further support for the pathological effect of increased amount of AFF3 protein.\n\nWhereas homozygous Aff3 knockout mice display skeletal anomalies, kidney defects, brain malformation and neurological anomalies, knock-in animals modeling the microdeletion and the missense variants identified in affected individuals presented with lower mesomelic limb deformities and early lethality, respectively.\n\nTranscriptome analyses as well as the partial phenotypic overlap of syndromes associated with AFF3 and AFF4 variants suggest that ALF transcription factors are not redundant in contrast to what was previously suggested

genetics↗