Biology subjects

De La Cruz, N.

Publications and source records attributed to De La Cruz, N..

5 recordsLinked to original sources

bioRxiv2026

Reconstituting Mouse Embryogenesis Ex Utero from Gastrulation to Fetal Development Reveals Maternally Independent Metabolic Programs

Mammalian development takes place inside the maternal uterus, creating technological constraints that make difficult the study of embryogenesis in live developing embryos. A central challenge for understanding the role of metabolism in mammalian development is discriminating placental and uterine-regulated signals from embryo-intrinsic processes independent of maternal influence, a process that until now has remained inseparable during gastrulation and organogenesis1-3. Ex utero culture systems allowing continuous growth of embryos during pre-gastrulation to organogenesis4,5 offer a promising solution to this challenge. Here, we present optimized ex utero culture platforms that support faithful development of mouse embryos from gastrulation (embryonic day 6.5/7.5) through the fetal period (embryonic day [~]12.5) and harnessed these platforms for dissecting metabolic transitions in vivo during embryogenesis independently of uterus and placenta. We characterized the metabolome of in utero and ex utero whole embryos, fetal organs and culture medium between embryonic days E6.5 and E12.5 by liquid chromatography mass-spectrometry (LC-MS) metabolomics, isotope tracing, and single cell transcriptomics. These datasets present a comprehensive overview of the dynamic embryonic metabolism during gastrulation and organogenesis in utero and ex utero. This analysis revealed that the midgestational metabolic switch occurring at E10.5-E11.5 is faithfully recapitulated ex utero, indicating that this transition is intrinsically programmed in embryonic tissues and does not require direct maternal or placental cues. Notably, oxygen availability modulated the extent of this transition, but elevated oxygen was insufficient to induce it prematurely, demonstrating that the switch is developmentally timed and only partially environmental-responsive. We further harnessed the ex utero platform for identifying and perturbing a mitochondrial redox shift at E7.5-E8.5 that is critical for developmental progress after gastrulation. These findings uncover the remarkable metabolic plasticity of the mammalian embryo, demonstrating its capacity to sustain growth independently of maternal inputs from the establishment of the body plan through the onset of the fetal period. Moreover, they highlight the use of long-term ex utero culture as a unique framework for dissecting the mechanisms that shape embryogenesis under physiological and experimentally perturbed conditions, while functionally uncoupling embryonic programs from maternal and placental influences.

developmental biology↗

bioRxiv2026

Midgestation metabolic constraint in purine metabolism drives distinct strategies for placenta and fetal growth

Purine nucleotides are essential for mammalian development1,2. Purine monophosphates support cell signaling and proliferation and are synthesized by cells through either de novo synthesis or a salvage pathway3. We previously identified a midgestational metabolic transition in mice (gestational days gd10.5-11.5) characterized by changes in purine metabolism4. Midgestation is a period of rapid growth for placenta and embryo, yet it remains unclear how the placental tissues expand without directly competing with the embryo for biosynthetic resources. Here, we show that this midgestational metabolic transition is associated with a marked reduction in embryonic expression of purine salvage enzymes, which constrains embryonic metabolism and leads to different strategies for purine synthesis between the placenta and embryo. Midgestation embryos are unable to engage the purine salvage pathway even when de novo purine synthesis is blocked either in vivo or in ex utero embryo culture, whereas placental tissue and trophoblasts retain the capacity to use either pathway. Disruption of de novo purine synthesis in mice causes reduced embryonic growth, impaired axial elongation, and abnormal brain and placental development, which are only partially rescued by supplementation with purine salvage precursors. In human placenta, trophoblast stem cells readily switch between the de novo and salvage pathways based on nutrient availability, and syncytiotrophoblasts (STB) preferentially rely on the salvage pathway. We identified guanosine monophosphate (GMP) as a metabolic checkpoint regulating STB differentiation, with insufficient GMP levels causing degradation of the small GTPase Rheb and failure of mTOR activation. Supplementation of purine salvage substrates restored GMP synthesis and STB differentiation in humans, but not mice. Further, in vivo measurements in humans revealed that maternal circulating hypoxanthine decreases during pregnancy and is further reduced in women with clinically small placentas, highlighting the role of hypoxanthine in supporting placental growth. These results uncover compartmentalized purine salvage between the embryo and placenta as a mechanism that limits competition for biosynthetic resources and enables coordinated growth during mammalian development.

developmental biology↗

bioRxiv2025

Sequence-based prediction of condensate composition reveals that specificity can emerge from multivalent interactions among disordered regions

While specificity of biomolecular interactions is typically understood to require interactions involving ordered structures, several biomolecular condensates exhibit specificity in the absence of apparent structural order. We have previously shown that condensates composed of the disordered region of MED1 partition specific proteins, mediated by sequence patterns of charged amino acids on the disordered regions of both MED1 and the interacting partner. Whether this specificity is due to an unknown ordered-structure-mediated interaction or from the dynamic multivalent interactions between the patterned charged amino acids in the disordered regions was unresolved. Here we show that a polymer physics-based model that only accounts for multivalent interactions among polymers in a statistical manner can largely explain published data on selective partitioning and make predictions that are subsequently experimentally validated. These results suggest that the specificity of condensate composition is underpinned to a substantial extent by multivalent interactions in the context of conformational disorder.

biophysics↗

bioRxiv2024

Genomic Epidemiology of Monkeypox Virus During the 2022 Outbreak in New York City

New York City (NYC) was one of the hotspots of monkeypox virus (MPXV) infections in the United States during the multi-country mpox outbreak in 2022. This study used the most comprehensive dataset to date to investigate the genomic characteristics of MPXV in NYC. We performed Nextclade lineage assignment, phylogenetic and mutational analyses on 1,138 specimens from 748 individuals at the NYC Public Health Lab in the context of 2,968 MPXV sequences sampled globally. Nextclade lineage assignment showed B.1.12 as a NYC specific lineage and phylogenetic analysis showed NYC and North America specific clades. The majority of mutations showed signatures of APOBEC3 activity. When looking at the intra-host genomic diversity for MPXV, distinct MPXV genomic profiles were observed in 6.4% of individuals with multiple sampled specimens, with at least 4.2% of NYC cases due to multiple MPXV infections from distinct viral strains. Further, 13% of the sequences in infected patients had a lack of concordance between epidemiologic and genetic linkages. This study identified NYC-specific MPXV genomic profiles and provided a conservative estimate of simultaneous infections with multiple MPXV variants, likely due to behavioral risk factors during the peak of the outbreak in July 2022. Improving concordance between genomic and epidemiological clusters for mpox investigations may require expanding partnerships with testing labs, clinics, and community groups to enhance the representativeness of MPXV samples that are available for sequencing.

genomics↗

bioRxiv2024

N6-methyladenosine in DNA promotes genome stability

DNA base lesions, such as incorporation of uracil into DNA or base mismatches, can be mutagenic and toxic to replicating cells. To discover factors in repair of genomic uracil, we performed a CRISPR knockout screen in the presence of floxuridine, a chemotherapeutic agent that incorporates uracil and fluoro-uracil into DNA. We identified known factors, such as uracil DNA N-glycosylase (UNG), and unknown factors, such as the N6-adenosine methyltransferase, METTL3, as required to overcome floxuridine-driven cytotoxicity. Visualized with immunofluorescence, the product of METTL3 activity, N6-methyladenosine, formed nuclear foci in cells treated with floxuridine. The observed N6-methyladenosine was embedded in DNA, called 6mA, and these results were confirmed using an orthogonal approach, liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). METTL3 and 6mA were required for repair of lesions driven by additional base damaging agents, including raltitrexed, gemcitabine, and hydroxyurea. Our results establish a role for METTL3 and 6mA in promoting genome stability in mammalian cells, especially in response to base damage.

molecular biology↗