Biology subjects

Jimenez, E.

Publications and source records attributed to Jimenez, E..

6 recordsLinked to original sources

bioRxiv2023

Steroid signaling controls sex-specific development in an invertebrate

In vertebrate sexual development, two important steroid hormones, testosterone and estrogen, regulate the sex-specific development of many tissues. In contrast, invertebrates utilize a single steroid hormone, ecdysone, to regulate developmental timing in both sexes. However, here we show that in Drosophila melanogaster, sex-specific ecdysone (E) signaling controls important aspects of gonad sexual dimorphism. Rather than being regulated at the level of hormone production, hormone activity is regulated cell-autonomously through sex-specific hormone reception. Ecdysone receptor (EcR) expression is restricted to the developing ovary and is repressed in the testis at a time when ecdysone initiates ovary morphogenesis. Interestingly, EcR expression is regulated downstream of the sex determination factor Doublesex (Dsx), the founding member of the Dsx/Mab3 Related Transcription Factor (DMRT) family that regulates gonad development in all animals. E signaling is required for normal ovary development1,2, and ectopic activation of E signaling in the testis antagonized stem cell niche identity and feminized somatic support cells, which were transformed into follicle-like cells. This work demonstrates that invertebrates can also use steroid hormone signaling to control sex-specific development. Further, it may help explain recent work showing that vertebrate sexual development is surprisingly cell-autonomous. For example, chickens utilize testosterone and estrogen to control sex-specific development, but when they have a mixture of cells with male and female genotypes, the male cells develop as male and the female cells develop as female despite exposure to the same circulating hormones3. Sex-specific regulation of steroid hormone signaling may well underly such cell-autonomous sexual fate choices in vertebrates as it does in Drosophila.

developmental biology↗

bioRxiv2022

SPACA6 structure reveals a conserved superfamily of gamete fusion-associated proteins

SPACA6 is a sperm-expressed surface protein that is critical for gamete fusion during mammalian sexual reproduction. Despite this fundamental role, little is known about how SPACA6 specifically functions. We elucidated the crystal structure of SPACA6 at 2.2-[A] resolution, revealing a two-domain protein containing a four-helix bundle and Ig-like {beta}-sandwich connected via a quasi-flexible linker. Based on the structural analysis, we propose SPACA6 is a founding member of a superfamily of gamete fusion-associated proteins, herein dubbed the IST superfamily. The IST superfamily is defined structurally by its distorted four-helix bundle and a pair of disulfide-bonded CXXC motifs. A structure-based search of the AlphaFold human proteome identified more protein members to this superfamily; remarkably, many of these proteins are linked to gamete fusion. The SPACA6 structure and its connection to other IST-superfamily members provide a missing link in our knowledge of mammalian gamete fusion. Significance StatementSPACA6 is a human sperm protein vital for the fusion of gametes, though its exact function remains a mystery. We present the first solved structure of SPACA6: a two-domain fold comprised of an Ig-like domain and a distorted four-helix bundle. Dali searches of the PDB and AlphaFold reveal a family of structurally related proteins, several of which are also known to play a role in gamete fusion; as such, SPACA6 is a founding member of a conserved protein superfamily, dubbed the IST superfamily. Evolutionary analysis to ascertain functionally relevant structural elements in SPACA6 show a conservation of flexibility between the two domains and several conserved surfaces that could function as protein-protein interfaces.

developmental biology↗

bioRxiv2022

A regulatory network of Sox and Six transcription factors initiate a cell fate transformation during hearing regeneration in adult zebrafish

Using adult zebrafish inner ears as a model for sensorineural regeneration, we performed a targeted ablation of the mechanosensory receptors in the utricle and saccule and characterized the single-cell epigenome and transcriptome at consecutive time-points following hair cell ablation. Using deep learning on the regeneration-induced open chromatin sequences, we were able to identify unique, cell-specific transcription factor (TF) motif patterns enriched in the raw data. We correlated enhancer activity with gene expression to identify gene regulatory networks. A clear pattern of overlapping Sox- and Six-family transcription factor gene expression and binding motifs was detected, suggesting a combinatorial program of TFs driving regeneration and cell identity. Pseudo-time analysis of single-cell transcriptomic data demonstrated that the support cells within the sensory epithelium changed cell identity to a more pluripotent "progenitor" cell population that could either differentiate into hair cells or return to a support cell identity. We showed that sox2 becomes enriched in the progenitor cells and is reduced again when the cells differentiate in either direction. Analysis of the scATAC-seq data identified a 2.6 kb DNA sequence element upstream of the sox2 promoter that dynamically changed in accessibility during hair cell regeneration. When deleted, the upstream regulator of sox2 showed a dominant phenotype that resulted in a hair cell regeneration-specific deficit in both the lateral line and adult inner ear. HIGHLIGHTSIntegrated scRNA-seq and scATAC-seq of the adult zebrafish inner ear during hair cell regeneration. Support cells transition to an intermediate cell type that can differentiate to hair cells. Coordinated expression of Sox and Six transcription factors are key to hearing regeneration. Sox transcription factors trigger the regeneration response in the support cells while Sox and Six factors cooperate during hair cell differentiation. Deletion of an upstream enhancer that controls the timing of sox2 expression causes regeneration-specific defects in hearing regeneration.

genomics↗

bioRxiv2021

Vestibular and auditory hair cell regeneration following targeted ablation of hair cells with diphtheria toxin in zebrafish

Millions of Americans experience hearing or balance disorders due to loss of hair cells in the inner ear. The hair cells are mechanosensory receptors used in the auditory and vestibular organs of all vertebrates as well as the lateral line systems of aquatic vertebrates. In zebrafish and other non-mammalian vertebrates, hair cells turn over during homeostasis and regenerate completely after being destroyed or damaged by acoustic or chemical exposure. However in mammals, destroying or damaging hair cells results in permanent impairments to hearing or balance. We sought an improved method for studying hair cell damage and regeneration in adult aquatic vertebrates by generating a transgenic zebrafish with the capacity for targeted and inducible hair cell ablation in vivo. This model expresses the human diphtheria toxin receptor (hDTR) gene under the control of the myo6b promoter, resulting in hDTR expressed only in hair cells. Cell ablation is achieved by an intraperitoneal injection of diphtheria toxin (DT) in adult zebrafish or DT dissolved in the water for larvae. In the lateral line of 5 dpf zebrafish, ablation of hair cells by DT treatment occurred within 2 days in a dose-dependent manner. Similarly, in adult utricles and saccules, a single intraperitoneal injection of 0.05 ng DT caused complete loss of hair cells in the utricle and saccule by 5 days post-injection. Full hair cell regeneration was observed for the lateral line and the inner ear tissues. This study introduces a new method for efficient conditional hair cell ablation in adult zebrafish inner ear sensory epithelia (utricles and saccules) and demonstrates that zebrafish hair cells will regenerate in vivo after this treatment.

developmental biology↗

bioRxiv2019

A model for reticular dysgenesis shows impaired sensory organ development and hair cell regeneration linked to cellular stress

Mutations in the gene AK2 are responsible for Reticular Dysgenesis (RD), a rare and severe form of primary immunodeficiency in children. RD patients have a severely shortened life expectancy and without treatment die a few weeks after birth. The only available therapeutic option for RD is bone marrow transplantation. To gain insight into the pathophysiology of RD, we previously created zebrafish models for an AK2 deficiency. One of the clinical features of RD is hearing loss, but its pathology and causes have not been determined. In adult mammals, sensory hair cells of the inner ear do not regenerate; however, their regeneration has been observed in several non-mammalian vertebrates, including zebrafish. Therefore, we use our RD zebrafish models to determine if AK2 deficiency affects sensory organ development and/or hair cell regeneration. Our studies indicated that AK2 is required for the correct development, survival and regeneration of sensory hair cells. Interestingly, AK2 deficiency induces the expression of several oxidative stress markers and it triggers an increased level of cell death in the hair cells. Finally, we show that glutathione treatment can partially rescue hair cell development in the sensory organs in our RD models, pointing to the potential use of antioxidants as a supportive therapeutic modality for RD patients, not only to increase their chances of survival, but to prevent or ameliorate their sensorineural hearing deficits.

developmental biology↗

bioRxiv2016

Highly-efficient Cpf1-mediated gene targeting in mice following high concentration pronuclear injection

Cpf1 has emerged as an alternative to the Cas9 RNA-guided nuclease. Here we show that gene targeting rates in mice using Cpf1 can meet or even surpass Cas9 targeting rates (approaching 100% targeting) but require higher concentrations of mRNA and guide. We also demonstrate that co-injecting two guides with close targeting sites can result in synergistic genomic cutting, even if one of the guides has minimal cutting activity.

genetics↗