Biology subjects

Luo, J.-D.

Publications and source records attributed to Luo, J.-D..

8 recordsLinked to original sources

bioRxiv2025

Short-term gonadal cultures are sufficient for germline transmission in a songbird

1Primordial germ cells (PGCs) are germline stem cells that develop into sperm or egg cells and are valuable for avian biobanking and the propagation of donor-derived offspring. However, in non-poultry birds the long-term maintenance and self-renewal of PGCs in vitro remains challenging. This limitation hinders biobanking in other avian clades, particularly in the zebra finch and other songbirds that uniquely possess a germline restricted chromosome (GRC). Here, we generated and compared short-term cultures of chicken and zebra finch PGCs from the embryonic gonads or blood, as well as established long-term cultures of chicken PGCs. Using single-cell RNA sequencing, we found that the transcriptome profile of long-term chicken gonadal cultures were exclusively PGCs, whereas the short-term chicken and zebra finch cultures represented a heterogeneous mixture of cell types. The zebra finch culture further included rapidly differentiating PGCs, as well as a germ cell type not previously identified in the embryonic songbird gonad. Although zebra finch short-term gonadal cultures did not yield robust long-term PGC cultures, short-term cultured PGCs were able to integrate into host zebra finch gonads after injection into the dorsal aorta, contribute to gametic populations in adult chimeras, and give rise to phenotypically- and genomically-validated offspring. This study provides a foundation for using short-term gonadal cultures to derive donor and transgenic offspring in songbirds and further explore the unique developmental genetics of PGCs across the avian clade. SummaryBeyond poultry, the long-term culture of self-renewing primordial germ cells (PGCs) remains a challenge. Here, we compare the cell population heterogeneity and reproductive viability of gonadal cultures for the zebra finch, a songbird model of vocal learning, with established chicken PGC protocols. Using single-cell RNA sequencing, we identify the rapid differentiation of zebra finch gonadal germ cells in vitro, including germline identities not previously noted in the embryonic gonad. In comparison, these differentiated cell profiles were also found in zebra finch blood PGC culture conditions, but not identified in short- or long-term chicken PGC cultures. Host embryo injections of these short-term zebra finch gonadal cultures resulted in germline chimeric animals, but at lower rates of gonadal reconstitution compared to chicken. Nonetheless, these cultures allowed for the derivation of zebra finch germline chimeras that yield phenotypically- and genomically-validated offspring from cultured PGCs.

developmental biology↗

bioRxiv2023

Pronounced early differentiation underlies zebra finch gonadal germ cell development.

The diversity of germ cell developmental strategies has been well documented across many vertebrate clades. However, much of our understanding of avian primordial germ cell (PGC) specification and differentiation has derived from only one species, the chicken (Gallus gallus). Of the three major classes of birds, chickens belong to Galloanserae, representing less than 4% of species, while nearly 95% of extant bird species belong to Neoaves. This represents a significant gap in our knowledge of germ cell development across avian species, hampering efforts to adapt genome editing and reproductive technologies developed in chicken to other birds. We therefore applied single-cell RNA sequencing to investigate inter-species differences in germ cell development between chicken and zebra finch (Taeniopygia castanotis), a Neoaves songbird species and a common model of vocal learning. Analysis of early embryonic male and female gonads revealed the presence of two distinct early germ cell types in zebra finch and only one in chicken. Both germ cell types expressed zebra finch Germline Restricted Chromosome (GRC) genes, present only in songbirds among birds. One of the zebra finch germ cell types expressed the canonical PGC markers, as did chicken, but with expression differences in several signaling pathways and biological processes. The second zebra finch germ cell cluster was marked by proliferation and fate determination markers, indicating beginning of differentiation. Notably, these two zebra finch germ cell populations were present in both male and female zebra finch gonads as early as HH25. Using additional chicken developmental stages, similar germ cell heterogeneity was identified in the more developed gonads of females, but not males. Overall, our study demonstrates a substantial heterochrony in zebra finch germ cell development compared to chicken, indicating a richer diversity of avian germ cell developmental strategies than previously known.

cell biology↗

bioRxiv2023

Cellular and Molecular Basis of Leptin Resistance

Obese humans and diet induced obese mice (DIO) have high leptin levels and fail to respond to the exogenous hormone suggesting that obesity is caused by leptin resistance, the pathogenesis of which is unknown. We found that leptin treatment reduced plasma levels of mTOR ligands leading us to hypothesize that mTOR activation might inhibit leptin signaling. Rapamycin, an mTOR inhibitor, reduced fat mass and increased leptin sensitivity in DIO mice but not in mice with defects in leptin signaling. Rapamycin restored leptins actions on POMC neurons but failed to reduce the weight of mice with defects in melanocortin signaling. mTOR activation in POMC neurons caused leptin resistance while POMC specific mutations in mTOR activators decreased the weight gain of DIO mice. Thus increased mTOR activity in POMC neurons is necessary and sufficient for the development of leptin resistance in DIO mice establishing a key pathogenic mechanism leading to obesity.

neuroscience↗

bioRxiv2023

Layer 5a Corticostriatal Projection Neurons are Selectively Vulnerable in Huntington's Disease

The properties of the cell types that are selectively vulnerable in Huntingtons disease (HD) cortex, the nature of somatic CAG expansions of mHTT in these cells, and their importance in CNS circuitry have not been delineated. Here we employed serial fluorescence activated nuclear sorting (sFANS), deep molecular profiling, and single nucleus RNA sequencing (snRNAseq) to demonstrate that layer 5a pyramidal neurons are vulnerable in primary motor cortex and other cortical areas of HD donors. Extensive mHTT-CAG expansions occur in vulnerable layer 5a pyramidal cells, and in Betz cells, layer 6a, layer 6b neurons that are resilient in HD. Retrograde tracing experiments in macaque brains identify the vulnerable layer 5a neurons as corticostriatal pyramidal cells. We propose that enhanced somatic mHTT-CAG expansion and altered synaptic function act together to cause corticostriatal disconnection and selective neuronal vulnerability in the HD cerebral cortex.

neuroscience↗

bioRxiv2023

Coevolution of the CDCA7-HELLS ICF-related nucleosome remodeling complex and DNA methyltransferases

5-Methylcytosine (5mC) and DNA methyltransferases (DNMTs) are broadly conserved in eukaryotes but are also frequently lost during evolution. The mammalian SNF2 family ATPase HELLS and its plant ortholog DDM1 are critical for maintaining 5mC. Mutations in HELLS, its activator CDCA7, and the de novo DNA methyltransferase DNMT3B, cause immunodeficiency-centromeric instability-facial anomalies (ICF) syndrome, a genetic disorder associated with the loss of DNA methylation. We here examine the coevolution of CDCA7, HELLS and DNMTs. While DNMT3, the maintenance DNA methyltransferase DNMT1, HELLS, and CDCA7 are all highly conserved in vertebrates and green plants, they are frequently co-lost in other evolutionary clades. The presence-absence patterns of these genes are not random; almost all CDCA7 harboring eukaryote species also have HELLS and DNMT1 (or another maintenance methyltransferase, DNMT5). Coevolution of presence-absence patterns (CoPAP) analysis in Ecdysozoa further indicates coevolutionary linkages among CDCA7, HELLS, DNMT1 and its activator UHRF1. We hypothesize that CDCA7 becomes dispensable in species that lost HELLS or DNA methylation, and/or the loss of CDCA7 triggers the replacement of DNA methylation by other chromatin regulation mechanisms. Our study suggests that a unique specialized role of CDCA7 in HELLS-dependent DNA methylation maintenance is broadly inherited from the last eukaryotic common ancestor.

evolutionary biology↗

bioRxiv2022

A tissue injury repair pathway distinct but parallel to host pathogen defense

Pathogen infection and tissue injury are universal insults that disrupt homeostasis. Innate immunity senses microbial infections and induces interferons (IFNs) to activate resistance mechanisms. Applying unbiased phylogenetic analysis, we show that interleukin-24 (IL24) is among the closest evolutionary homologs to the IFN family and shares a common ancestral origin. However, in contrast to IFNs, IL24 induction occurs specifically in barrier epithelial progenitors after injury and is independent of microbiome or adaptive immunity. Surprisingly, Il24 ablation impedes not only epidermal proliferation and re-epithelialization, but also capillary and fibroblast regeneration within the dermal wound bed. Conversely, ectopic Il24 induction in homeostatic epidermis triggers global epithelial-mesenchymal tissue repair responses. Mechanistically, sustained Il24 expression depends upon both IL24 receptor/STAT3 signaling and also hypoxia-stabilized HIF1, which converge following injury. Thus, parallel to the IFN-mediated innate immune sensing of pathogens to resolve infections, epithelial stem cells sense injury signals to orchestrate IL24-mediated tissue repair.

immunology↗

bioRxiv2021

Fanconi Anemia Pathway Deficiency Drives Copy Number Variation in Squamous Cell Carcinomas

Fanconi anemia (FA), a model syndrome of genome instability, is caused by a deficiency in DNA interstrand crosslink (ICL) repair resulting in chromosome breakage1-3. The FA repair pathway comprises at least 22 FANC proteins including BRCA1 and BRCA24-6, and protects against carcinogenic endogenous and exogenous aldehydes7-10. Individuals with FA are hundreds to thousands-fold more likely to develop head and neck (HNSCC), esophageal and anogenital squamous cell carcinomas (SCCs) with a median onset age of 31 years11. The aggressive nature of these tumors and poor patient tolerance of platinum and radiation-based therapy have been associated with short survival in FA11-16. Molecular studies of SCCs from individuals with FA (FA SCCs) have been limited, and it is unclear how they relate to sporadic HNSCCs primarily driven by tobacco and alcohol exposure or human papillomavirus (HPV) infection17. Here, by sequencing FA SCCs, we demonstrate that the primary genomic signature of FA-deficiency is the presence of a high number of structural variants (SVs). SVs are enriched for small deletions, unbalanced translocations, and fold-back inversions that arise in the context of TP53 loss. The SV breakpoints preferentially localize to early replicating regions, common fragile sites, tandem repeats, and SINE elements. SVs are often connected forming complex rearrangements. Resultant genomic instability underlies elevated copy number alteration (CNA) rates of key HNSCC-associated genes, including PIK3CA, MYC, CSMD1, PTPRD, YAP1, MXD4, and EGFR. In contrast to sporadic HNSCC, we find no evidence of HPV infection in FA HNSCC, although positive cases were identified in gynecologic tumors. A murine allograft model of FA pathway-deficient SCC was enriched in SVs, exhibited dramatic tumor growth advantage, more rapid epithelial-to-mesenchymal transition (EMT), and enhanced autonomous inflammatory signaling when compared to an FA pathway-proficient model. In light of the protective role of the FA pathway against SV formation uncovered here, and recent findings of FA pathway insufficiency in the setting of increased formaldehyde load resulting in hematopoietic stem cell failure and carcinogenesis18-20, we propose that high copy-number instability in sporadic HNSCC may result from functional overload of the FA pathway by endogenous and exogenous DNA crosslinking agents. Our work lays the foundation for improved FA patient treatment and demonstrates that FA SCC is a powerful model to study tumorigenesis resulting from DNA crosslinking damage.

cancer biology↗

bioRxiv2021

Role of YAP in early ectodermal specification anda Huntington's Disease model of human neurulation

The Hippo pathway, a highly conserved signaling cascade that functions as an integrator of molecular signals and biophysical states, ultimately impinges upon the transcription coactivator Yes-associated protein 1 (YAP). Hippo-YAP signaling has been shown to play key roles both at the early embryonic stages of implantation and gastrulation, and later during neurogenesis. To explore YAPs potential role in neurulation, we used self-organizing neuruloids grown from human embryonic stem cells on micropatterned substrates. We identified YAP activation as a key lineage determinant, first between neuronal ectoderm and non-neuronal ectoderm, and later between epidermis and neural crest, indicating that YAP activity can enhance the effect of BMP4 stimulation and therefore affect ectodermal specification at this developmental stage. Because aberrant Hippo-YAP signaling has been implicated in the pathology of Huntingtons Disease (HD), we used isogenic mutant neuruloids to explore the relationship between signaling and the disease. We found that HD neuruloids demonstrate ectopic activation of gene targets of YAP and that pharmacological reduction of YAPs transcriptional activity can partially rescue the HD phenotype.

developmental biology↗