Biology subjects

Tessarollo, L.

Publications and source records attributed to Tessarollo, L..

7 recordsLinked to original sources

bioRxiv2026

A single BRCA2 BRC repeat supports viability while multiple repeats ensure resilience under stress

BRC repeats are integral to BRCA2 function and mediate RAD51 loading during homologous recombination (HR). Their number varies across species, but mammals, including mice and humans, harbor eight repeats. Prior studies have suggested functional redundancy among these repeats, but the biological significance of maintaining multiple repeats remains unresolved. Here, we demonstrate that the presence of a single BRC repeat, either BRC2 or BRC4, is sufficient for mouse embryonic stem cell (mESC) viability, RAD51 loading, PARP inhibitor resistance and protection of stalled replication forks. Consistent with these findings, we show that knock-in mice with a single BRC repeat 2 or 4 are viable and exhibit normal growth and fertility. In contrast, embryonic fibroblasts from these mice display genomic instability and impaired RAD51 recruitment. Notably, this defect is rescued under low oxygen culture conditions, which mimics physoxic levels, whereas exposure to oxidative stress impairs RAD51 recruitment in mESCs harboring a single BRC repeat. Together, our findings indicate that while a single BRC repeat is sufficient under physiological conditions, the evolutionary retention of multiple BRC repeats likely ensures robust genome stability under extreme oxidative stress.

genetics↗

bioRxiv2025

Pde5a Deficiency Prevents Diet-Induced Obesity via Adipose cAMP-PKA Activation Enhancing Fat Browning

Cyclic nucleotides are critical regulators of adaptive thermogenesis and adipogenesis, with their intracellular levels finely tuned by phosphodiesterases. Phosphodiesterase type 5 (PDE5A) modulates cyclic guanosine monophosphate levels in adipocytes. While PDE5A inhibition has shown promise in patients with diabetes, its role in metabolism remains unclear. Using Pde5a knockout mouse models, we demonstrated that mice lacking Pde5a exhibit enhanced browning of white adipose tissue and reduced hepatic fat content. Following high-fat diet, Pde5a-/- mice are resistant to obesity, displaying improved glucose metabolism and enhanced thermogenesis. These protective effects stem from an early developmental knockdown of Pde5a, leading to a metabolic reprogramming driven by cAMP-PKA pathway activation. The convergence of cGMP and cAMP signaling orchestrates thermogenic and systemic metabolic adaptations. Our findings establish PDE5A as a novel regulator of energy homeostasis, suggesting its inhibition as a valuable adjuvant therapy for metabolic disorders.

cell biology↗

bioRxiv2024

Clusters of deep intronic RbFox motifs regulate mammalian alternative splicing

The RbFox RNA binding proteins regulate alternative splicing of genes governing mammalian development and organ function. They bind to the RNA sequence (U)GCAUG with high affinity but also non-canonical secondary motifs in a concentration dependent manner. However, the hierarchical requirement of RbFox motifs, which are widespread in the genome, is still unclear. Here we show that deep intronic, tightly clustered RbFox1 motifs cooperate and are important regulators of alternative exons splicing. Bioinformatic analysis revealed that (U)GCAUG-clusters are widely present in both mouse and human genes and are embedded in sequences binding the large assembly of splicing regulators (LASR). Integrative data analysis from eCLIP and RNAseq experiments showed a global increase in RNA isoform modulation of genes with Rbfox1 eCLIP-peaks associated with these clusters. Experimentally, by employing recombineering mutagenesis in a bacterial artificial chromosome containing the NTrk2 mouse region subjected to alternative splicing we showed that tightly clustered (U)GCAUG motifs in the middle of 50 Kb introns are necessary for RbFox1 regulation of NTrk2 gene isoforms expression. Moreover, clustered (U)GCAUG-motifs promote the recruitment of RbFox1 proteins to form a Rbfox1/LASR complex required for splicing. These data suggest that clustered, distal intronic Rbfox-binding motifs embedded in LASR binding sequences are important determinants of RbFox1 function in the mammalian genome and provide a target for identification of pathogenic mutations.

genetics↗

bioRxiv2022

3'UTR-directed, kinase proximal mRNA decay inhibits C/EBPβ phosphorylation/activation to suppress senescence in tumor cells

C/EBP{beta} is a potent regulator of oncogene-induced senescence (OIS) and the SASP. C/EBP{beta} is post-translationally activated in OIS cells by the effector kinases ERK1/2 and CK2. However, in tumor cells C/EBP{beta} activation is suppressed by its 3UTR. 3'UTR regulation of protein activity (UPA) requires a G/U-rich element (GRE) and its cognate binding protein, HuR. These components segregate CEBPB transcripts away from a perinuclear compartment harboring ERK1/2 and CK2, restricting C/EBP{beta} from its activating kinases. We report here that the mRNA decay proteins UPF1 and Staufen1/2 are essential UPA factors enriched within the perinuclear cytoplasm. STAU1/2 and UPF1 overlap with CK2 on perinuclear signaling endosomes where they promote localized CEBPB mRNA decay. UPF1 or STAU1/2 depletion in tumor cells increased CEBPB transcripts adjacent to CK2 foci, coinciding with C/EBP{beta} activation and senescence. The GRE and an adjacent STAU binding site independently suppress C/EBP{beta}-mediated senescence, while a distinct 3UTR region inhibits its SASP-inducing activity. KrasG12D-driven lung tumors in mice carrying a Cebpb GRE deletion rarely progressed to malignant adenocarcinomas, demonstrating the importance of UPA to enable tumor progression in vivo. Thus, kinase-proximal mRNA decay is a novel mechanism that inhibits C/EBP{beta} activation in tumor cells to facilitate senescence bypass.

cancer biology↗

bioRxiv2021

Multimeric nanobodies from camelid engineered mice and llamas potently neutralize SARS-CoV-2 variants

Since the start of the coronavirus disease-2019 (COVID-19) pandemic, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has caused more than 2 million deaths worldwide. Multiple vaccines have been deployed to date, but the continual evolution of the viral receptor-binding domain (RBD) has recently challenged their efficacy. In particular, SARS-CoV-2 variants originating in the U.K. (B.1.1.7), South Africa (B.1.351) and New York (B.1.526) have reduced neutralization activity from convalescent sera and compromised the efficacy of antibody cocktails that received emergency use authorization. Whereas vaccines can be updated periodically to account for emerging variants, complementary strategies are urgently needed to avert viral escape. One potential alternative is the use of camelid VHHs (also known as nanobodies), which due to their small size can recognize protein crevices that are inaccessible to conventional antibodies. Here, we isolate anti-RBD nanobodies from llamas and "nanomice" we engineered to produce VHHs cloned from alpacas, dromedaries and camels. Through binding assays and cryo-electron microscopy, we identified two sets of highly neutralizing nanobodies. The first group expresses VHHs that circumvent RBD antigenic drift by recognizing a region outside the ACE2-binding site that is conserved in coronaviruses but is not typically targeted by monoclonal antibodies. The second group is almost exclusively focused to the RBD-ACE2 interface and fails to neutralize pseudoviruses carrying the E484K or N501Y substitutions. Notably however, they do neutralize the RBD variants when expressed as homotrimers, rivaling the most potent antibodies produced to date against SARS-CoV-2. These findings demonstrate that multivalent nanobodies overcome SARS-CoV-2 variant mutations through two separate mechanisms: enhanced avidity for the ACE2 binding domain, and recognition of conserved epitopes largely inaccessible to human antibodies. Therefore, while new SARS-CoV-2 mutants will continue to emerge, nanobodies represent promising tools to prevent COVID-19 mortality when vaccines are compromised.

immunology↗

bioRxiv2020

Phox2a defines a developmental origin of the anterolateral system in mice and humans

Anterolateral system neurons relay pain, itch and temperature information from the spinal cord to pain-related brain regions, but the differentiation of these neurons and their specific contribution to pain perception remain poorly defined. Here, we show that virtually all mouse spinal neurons that embryonically express the autonomic system-associated Paired-like homeobox 2A (Phox2a) transcription factor innervate nociceptive brain targets, including the parabrachial nucleus and the thalamus. We define Phox2a anterolateral system neuron birth order, migration and differentiation, and uncover an essential role for Phox2a in the development of relay of nociceptive signals from the spinal cord to the brain. Finally, we also demonstrate that the molecular identity of Phox2a neurons is conserved in the human foetal spinal cord. The developmental expression of Phox2a as a uniting feature of anterolateral system neurons suggests a link between nociception and autonomic nervous system function.

neuroscience↗

bioRxiv2017

Zfp423, A Joubert Syndrome Gene, Is A Domain-Specific Regulator Of Cell Cycle Progression, DNA Damage Response And Purkinje Cell Development In The Cerebellar Primordium

Neurogenesis is a tightly regulated process whose success depends on the ability to balance the expansion/maintenance of an undifferentiated neural progenitor pool with the precisely timed birth of sequential generations of neurons. The Zfp423 gene encodes a 30-Zn-finger transcription factor (TF) that acts as a scaffold in the assembly of complex transcriptional and cellular machineries regulating neural development. While null mutants for Zfp423 feature a severe cerebellar hypoplasia, the underlying mechanism is only partially characterized. Mutations of the human ortholog ZNF423 have been identified in patients carrying cerebellar vermis hypoplasia (CVH) or Joubert Syndrome (JS), associated with other signs of classical ciliopathy outside the central nervous system (CNS). ZNF423 also plays a role in the DNA damage response (DDR). To further characterize the role of ZFP423 in cerebellar neurogenesis, with a focus on Purkinje cells (PC) development, we analyzed two previously undescribed mutant mouse lines carrying allelic in-frame deletions of the corresponding gene, selectively affecting two functionally characterized protein-protein interaction domains, affecting zinc (Zn) fingers 9-20 or 28-30. Some phenotypic defects are allele specific: Zfp423{Delta}9-20/{Delta}9-20 mutants exhibit a depletion of the OLIG2+ PC progenitor pool in the cerebellar ventricular zone (VZ). In these mutants, M-phase progenitors display changes in spindle orientation indicative of a precocious switch from symmetric to asymmetric cell division. Conversely, the Zfp423{Delta}28-30/{Delta}28-30 primordium displays a sharp decrease in the expression of PC differentiation markers, including CORL2, despite an abundance of cycling PC progenitors. Moreover, and importantly, in both mutants VZ progenitor cell cycle progression is remarkably affected, and factors involved in the DDR are substantially upregulated in the VZ and in postmitotic precursors alike. Our in vivo evidence sheds light on the domain-specific roles played by ZFP423 in different aspects of PC progenitor development, and at the same time supports the emerging notion that an impaired DNA damage response may be a key factor in the pathogenesis of JS and other ciliopathies.

neuroscience↗