Roberta Menafra

Hearing and balance rely on coordinated activity of multiple inner ear cell types, yet the mechanisms governing their development and specification in humans remain unclear. Consequently, this limits our understanding of how disease genes affect cell type formation and function, limiting the development of targeted treatments, including gene therapies. Here we present the Human Inner Ear Development snRNA-seq Atlas (HIEDRA), a single-nucleus transcriptomic atlas of the human inner ear spanning the first and second trimesters. HIEDRA maps sensory and nonsensory epithelia, neurons and mesenchyme-associated populations, including undercharacterized secretory cells required for ion homeostasis. We identify selective vulnerability in sensory and secretory lineages to disease-associated genes, infer regulatory networks and show that Hedgehog signaling suppression is required for secretory cell specification. We validate this mechanism in human inner ear organoids, expanding the model to include all major cell types. Altogether, these findings provide insights into human inner ear cell type specification, improve in vitro models and establish HIEDRA as a resource for investigating human inner ear development.

Pathological USH2A mutations cause Usher syndrome type II, characterized by progressive retinitis pigmentosa and hearing and balance impairment. This study aims to investigate the cellular mechanisms underlying USH2A-related retinal degeneration using human induced pluripotent stem cell (hiPSC)-derived retinal organoids. The introduction of a homozygous nonsense mutation in the USH2A hotspot exon-13 resulted in normal photoreceptor development but loss of ciliary localization of usherin long form B and its interacting proteins, ADGRV1 and whirlin. Notably, single-cell RNA sequencing revealed unexpected significant transcriptional changes in Müller glial cells (MGCs), suggestive of disruptions in the translation, innate immune response, and endolysosomal system. These findings suggest that, while photoreceptor cells are mildly affected by the exon-13 USH2A mutation, MGCs exhibit major transcriptional changes, potentially contributing to the disease progression and therefore shedding light on potential alternative therapeutic targets.

Loss-of-function variants in PALB2 give rise to defects in DNA damage repair by homologous recombination (HR), increasing the risk of breast cancer in female carriers. However, genetic testing frequently reveals missense variants of uncertain significance (VUS) for which the impact on protein function and cancer risk are unclear. Here we assay 84% of all possible missense variants in 11 out of 13 PALB2 exons using site-saturation functional screens with PARP inhibitor sensitivity as a readout for HR. These exons encode the coiled-coil and WD40 domains, which we identify as the minimal regions required for HR. Furthermore, we reveal the functional impact of 6718 missense variants, classifying 3904 variants as functional (58%), 2422 as intermediate (36%), and 392 as damaging (6%). A burden-type analysis shows that damaging missense variants in PALB2 are associated with a significantly increased risk of breast cancer, similar to that observed for truncating variants. These results will be valuable for the classification of PALB2 missense VUS and clinical management of carriers.

Pathological USH2A mutations cause Usher Syndrome type II, characterized by progres-sive retinitis pigmentosa and hearing and balance impairment. This study aims to inves-tigate the cellular mechanisms underlying USH2A-related retinal degeneration using hu-man induced pluripotent stem cell (hiPSC)-derived retinal organoids. The introduction of a homozygous nonsense mutation in the USH2A hotspot exon-13 resulted in normal photoreceptor development, but loss of ciliary localization of usherin long form B and its interacting proteins, ADGRV1 and whirlin. Notably, single-cell RNA sequencing revealed unexpected significant changes in Müller glial cells (MGCs), with disruptions in the translation, innate immune response, and endolysosomal system. These findings suggest that, while photoreceptor cells are mildly affected by the exon-13 USH2A mutation, MGCs exhibit major dysfunction, potentially contributing to the disease progression and there-fore shedding light on potential alternative therapeutic targets.

BRCA1 (breast cancer-associated protein 1) plays a central role in homologous recombination (HR) through interactions with multiple proteins across its various domains. The C-terminal BRCT domains bind HR regulators such as ABRAXAS1, CtIP, and BRIP1, each contributing to distinct, sometimes opposing, functions. While pathogenic mutations frequently cluster within the canonical BRCT phospho-binding pocket, the broader mutational landscape and its functional consequences remain poorly understood. Here, we used a site-saturation mutagenesis library of the BRCT domains to test >4,000 single-residue variants for their ability to bind ABRAXAS1 and CtIP. Using a yeast two-hybrid screen, we systematically assessed these interactions and validated key findings in mammalian cells. The resulting interaction map identified previously uncharacterized residues critical for partner binding and demonstrated their detrimental impact on HR. Importantly, we identified separation-of-function mutations that selectively disrupt individual protein interactions, enabling a more detailed analysis of each partner’s contribution to HR. Functional assays suggested that disruption of CtIP binding had the most pronounced impact on HR. Furthermore, integration of our data with clinical variant data revealed a strong correlation between loss of protein binding and pathogenicity, highlighting the potential utility of our interaction map for clinical variant interpretation.

Urbanization affects environmental exposures and lifestyle, shaping immune system variation and influencing disease susceptibility and vaccine responses. Here, we present systems analysis of immune profiles across the rural-urban gradient, comparing rural and urban Senegalese with urban Dutch individuals. By integrating single-cell phenotyping, metabolic profiling, and functional analysis, we reveal a trajectory of immune remodeling along the gradient. This includes enrichment of proinflammatory CD11c ⁺ B cells associated with altered IgG Fc glycosylation, adaptive NK cells with reduced responsiveness to accessory cytokines, and CD161 ⁺ CD4 ⁺ T cells with enhanced cytokine production in rural settings. Metabolic perturbation studies demonstrated distinct dependencies on glycolysis, pentose phosphate pathway, and fatty acid synthesis for cellular cytokine responses across populations. We validate core rural-urban immune signatures in an independent Indonesian cohort, suggesting shared immunological adaptations to urbanization across ancestries and geographical areas. Our findings provide insights into rural-urban immune function in understudied populations.

Although absence of interleukin-7 (IL-7) signaling completely abrogates T and B lymphopoiesis in mice, patients with severe combined immunodeficiency caused by mutations in the IL-7 receptor α chain (IL-7Rα) still generate peripheral blood B cells. Consequently, human B lymphopoiesis has been thought to be independent of IL-7 signaling. Using flow cytometric analysis and single-cell RNA sequencing of bone marrow samples from healthy controls and patients who are IL-7Rα deficient, in combination with in vitro modeling of human B-cell differentiation, we demonstrate that IL-7R signaling plays a crucial role in human B lymphopoiesis. IL-7 drives proliferation and expansion of early B-cell progenitors but not of pre-BII large cells and has a limited role in the prevention of cell death. Furthermore, IL-7 guides cell fate decisions by enhancing the expression of BACH2, EBF1, and PAX5, which jointly orchestrate the specification and commitment of early B-cell progenitors. In line with this observation, early B-cell progenitors of patients with IL-7Rα deficiency still expressed myeloid-specific genes. Collectively, our results unveil a previously unknown role for IL-7 signaling in promoting the B-lymphoid fate and expanding early human B-cell progenitors while defining important differences between mice and humans. Our results have implications for hematopoietic stem cell transplantation strategies in patients with T− B+ severe combined immunodeficiency and provide insights into the role of IL-7R signaling in leukemogenesis.

Innate mononuclear phagocytic system (MPS) cells preserve mucosal immune homeostasis. We investigated their role at nasal mucosa following allergen challenge with house dust mite. We combined single-cell proteome and transcriptome profiling on nasal immune cells from nasal biopsies cells from 30 allergic rhinitis and 27 non-allergic subjects before and after repeated nasal allergen challenge. Biopsies of patients showed infiltrating inflammatory HLA-DRhi/CD14+ and CD16+ monocytes and proallergic transcriptional changes in resident CD1C+/CD1A+ conventional dendritic cells (cDC)2 following challenge. In contrast, non-allergic individuals displayed distinct innate MPS responses to allergen challenge: predominant infiltration of myeloid-derived suppressor cells (MDSC: HLA-DRlow/CD14+ monocytes) and cDC2 expressing inhibitory/tolerogenic transcripts. These divergent patterns were confirmed in ex vivo stimulated MPS nasal biopsy cells. Thus, we identified not only MPS cell clusters involved in airway allergic inflammation but also highlight novel roles for non-inflammatory innate MPS responses by MDSC to allergens in non-allergic individuals. Future therapies should address MDSC activity as treatment for inflammatory airway diseases.

The use of pharmacogenomics in clinical practice is becoming standard of care. However, due to the complex genetic makeup of pharmacogenes, not all genetic variation is currently accounted for. Here, we show the utility of long-read sequencing to resolve complex pharmacogenes by analyzing a well-characterised sample. This data consists of long reads that were processed to resolve phased haploblocks. 73% of pharmacogenes were fully covered in one phased haploblock, including 9/15 genes that are 100% complex. Variant calling accuracy in the pharmacogenes was high, with 99.8% recall and 100% precision for SNVs and 98.7% precision and 98.0% recall for Indels. For the majority of gene-drug interactions in the DPWG and CPIC guidelines, the associated genes could be fully resolved (62% and 63% respectively). Together, these findings suggest that long-read sequencing data offers promising opportunities in elucidating complex pharmacogenes and haplotype phasing while maintaining accurate variant calling.