Biology subjects

Santi, C.

Publications and source records attributed to Santi, C..

3 recordsLinked to original sources

bioRxiv2026

Structural Insights into the Integration of Temperature and pH by Sperm Calcium Channel CatSper

The cation channel of sperm (CatSper) is a sperm-specific calcium channel essential for male fertility across metazoans. Its activation is tightly restricted to defined physiological contexts, including intracellular alkalinization, membrane depolarization, and elevated temperature. The structural and evolutionary mechanisms underlying this polymodal integration remain poorly understood, in part due to the architectural complexity of CatSper, a [~]15-subunit assembly organized in zigzag arrays along the sperm flagellum. Here we combine comparative genomics across 47 species with AlphaFold3-based modeling and evolutionary sequence-structure analyses to uncover a mechanism for temperature and pH integration. We identify the pore-forming subunit CatSper1 as an evolutionary hotspot exhibiting exceptional divergence in its N-terminal domain. Phylogenetic analysis shows that N-terminal length and histidine enrichment scale with species-specific fertilization temperatures, suggesting adaptive tuning of physicochemical sensitivity. Structural modeling indicates that conserved surface-exposed histidine clusters form inter-complex coupling interfaces between adjacent CatSper assemblies positioned near the dominant voltage-sensing module. Functional validation using electrophysiology and calcium imaging in mouse sperm shows that capacitation-associated partial removal of the CatSper1 N-terminus selectively impairs temperature-dependent activation. Together, these findings support a model in which temperature-dependent histidine deprotonation modulates supramolecular CatSper assembly to coordinate channel activation.

physiology↗

bioRxiv2023

The effect of Dnaaf5 gene dosage on primary ciliary dyskinesia phenotypes

DNAAF5 is a dynein motor assembly factor associated with the autosomal heterogenic recessive condition of motile cilia, primary ciliary dyskinesia (PCD). The effects of allele heterozygosity on motile cilia function are unknown. We used CRISPR-Cas9 genome editing in mice to recreate a human missense variant identified in patients with mild PCD and a second, frameshift null deletion in Dnaaf5. Litters with Dnaaf5 heteroallelic variants showed distinct missense and null gene dosage effects. Homozygosity for the null Dnaaf5 alleles was embryonic lethal. Compound heterozygous animals with the missense and null alleles showed severe disease manifesting as hydrocephalus and early lethality. However, animals homozygous for the missense mutation had improved survival, with partial preserved cilia function and motor assembly observed by ultrastructure analysis. Notably, the same variant alleles exhibited divergent cilia function across different multiciliated tissues. Proteomic analysis of isolated airway cilia from mutant mice revealed reduction in some axonemal regulatory and structural proteins not previously reported in DNAAF5 variants. While transcriptional analysis of mouse and human mutant cells showed increased expression of genes coding for axonemal proteins. Together, these findings suggest allele-specific and tissue-specific molecular requirements for cilia motor assembly that may affect disease phenotypes and clinical trajectory in motile ciliopathies. Brief SummaryA mouse model of human DNAAF5 primary ciliary dyskinesia variants reveals gene dosage effects of mutant alleles and tissue-specific molecular requirements for cilia motor assembly.

cell biology↗

bioRxiv2021

Soluble adenylyl cyclase inhibition prevents human sperm functions essential for fertilization

Soluble adenylyl cyclase (sAC: ADCY10) is essential for activating dormant sperm. Studies of freshly dissected mouse sperm identified sAC as needed for initiating capacitation and activating motility. We now use an improved sAC inhibitor, TDI-10229, for a comprehensive analysis of sAC function in human sperm. Unlike dissected mouse sperm, human sperm are collected post-ejaculation, after sAC activity has already been stimulated. Even in ejaculated human sperm, TDI-10229 interrupts stimulated motility and capacitation, and it prevents acrosome reaction in capacitated sperm. At present, there are no non-hormonal, pharmacological methods for contraception. Because sAC activity is required post-ejaculation at multiple points during the sperms journey to fertilize the oocyte, sAC inhibitors define candidates for non-hormonal, on-demand contraceptives suitable for delivery via intravaginal devices in females.

pharmacology and toxicology↗