Biology subjects

Shull, L.

Publications and source records attributed to Shull, L..

5 recordsLinked to original sources

bioRxiv2026

Loss of PRDM16 Drives Nasal Septal Deviation through Dysregulated TGFβ2 Signaling

Nasal septal deviation affects approximiately 20% of newborns globally and 80% individuals in the United States. GWAS have linked PRDM16, a histone methyltransferase, to craniofacial abnormalities, yet its role in nasal septum development remains poorly understood. Global Prdm16 knockout mice (Prdm16-/-) exhibit severe craniofacial defects resembling Pierre Robin Syndrome but are neonatally lethal, precluding their potential applications for postnatal study. To address this, we generated an osteochondral lineage-specific, Prdm16 conditional knockout (Col2a1-Cre; Prdm16flox/flox; cKO) mouse model. Both sexes of cKO mice display significantly shorter nasal bone length, with a sex-dependent increase in nasal bone volume fraction of 12 wk old males. Nasal septal deviation is detectable as early as postnatal day 15 and progresses with age. Single-cell RNA sequencing (scRNA-seq) of 4 wk old nasal septal cartilage revealed a marked shift in chondrocyte composition: Mgp+ chondrocytes were substantially reduced, while Col10a1+/Serpina3n+hypertrophic chondrocytes were dramatically increased, indicating PRDM16 regulates chondrocyte phenotypes. Spatial transcriptomics localized Mgp+ chondrocytes and Col1a1high/Col3a1+fibrotic cells to the septal cartilage-bone interface (the site of deviation in cKO mice). Intercellular communication analyses revealed a switch in dominant sender cells from the fibrotic population in WT to Mgp+chondrocytes in cKO. MultiNicheNet bioinformatic analyses identified elevated TGF{beta}2 signaling at the nasal septal deviation site. Specifically, TGF{beta}2 secreted by Mgp+ chondrocytes was predicted to promote Col1a1/Col1a2 expression, resulting in fibrotic extracellular matrix (ECM) deposition and osteogenesis; consistent with elevated RUNX2 in cKO mice. TGF{beta}2 immunohistochemical staining confirmed increased TGF{beta}2 cells in the fibrous ECM and apical nasal cartilage of cKO, but not WT mice. Loss of PRDM16 also increased chondrocyte apoptosis at 4 and 12 wks of age. These findings demonstrate that loss of PRDM16 drives hypertrophic and fibrotic remodeling of nasal septal cartilage through dysregulation of TGF{beta}2 signaling, establishing a mechanistic basis for nasal septal deviation.

developmental biology↗

bioRxiv2026

PRDM16 is necessary for sensory neuronal development in the Trigeminal Ganglion

BackgroundCranial neural crest cells (cNCC) generate craniofacial cartilage, bone, and peripheral neurons and glia, and birth defects arise when the cartilage/neuronal/glial progenitor fail to differentiate. PRDM16 is a transcriptional regulator containing both zinc-finger and SET domains, implicated in craniofacial development and orofacial clefting, but its role in cranial sensory ganglion formation has not been defined. ResultsHere, we demonstrate that prdm16 is required for trigeminal ganglion (TG) assembly and sensory neurogenesis from cranial neural crest lineages. In zebrafish, prdm16 is expressed in TG beginning by 18 hours post fertilization (hpf) and persists through the later developmental stage at 48 hpf. In the prdm16 loss-of-function zebrafish, fewer HuC+ TG neurons are present at 24 hpf and 48 hpf, along with reduced overall ganglion size. Live imaging in Tg(sox10:mRFP; elavl3:GFP) embryos demonstrates similar numbers of sox10+ cNCCs migrating to the TG region and reduced cell numbers and overall smaller size of TG in prdm16-/-. Acetylated {beta}-tubulin immunostaining shows fewer trigeminal axon projections early and an altered projection pattern by 48 hpf. A reduction in a defined sensory neuron population, p2rx3b+ cells displayed a weaker signal and decreased cell number in prdm16-/- TG. Transcriptomic analysis of FACS-isolated sox10+ cranial neural crest cells supported reduced expression of key neurogenic and sensory lineage genes. Finally, in mouse embryos, PRDM16 is expressed in TG neurons, and Prdm16csp1/csp1 embryos exhibited reduced TG volume, area and fewer HuC+ neurons at E18.5. ConclusionTogether, these data identify Prdm16 as a conserved regulator of trigeminal ganglion growth and sensory neuron differentiation, linking PRDM-family chromatin regulators to the development of the peripheral sensory nervous system.

developmental biology↗

bioRxiv2023

SPLIT HAND/FOOT VARIANTS FAIL TO RESCUE PRDM1A MUTANT CRANIOFACIAL DEFECTS

BackgroundSplit Hand/Foot Malformation (SHFM) is a congenital limb disorder presenting with limb anomalies, such as missing, hypoplastic, or fused digits, and often craniofacial defects, including a cleft lip/palate, microdontia, micrognathia, or maxillary hypoplasia. We previously identified three novel variants in the transcription factor, PRDM1, that are associated with SHFM phenotypes. One individual also presented with a high arch palate. Studies in vertebrates indicate that PRDM1 is important for development of the skull; however, prior to our study, human variants in PRDM1 had not been associated with craniofacial anomalies. MethodsUsing transient mRNA overexpression assays in prdm1a-/- mutant zebrafish, we tested whether the PRDM1 SHFM variants were functional and could lead to a rescue of the craniofacial defects observed in prdm1a-/- mutants. We also mined a CUT&RUN and RNA-seq dataset to examine Prdm1a binding and the effect of Prdm1a loss on craniofacial genes. Resultsprdm1a-/- mutants exhibit craniofacial defects including a hypoplastic neurocranium, a loss of posterior ceratobranchial arches, a shorter palatoquadrate, and an inverted ceratohyal. Injection of wildtype hPRDM1 in prdm1a-/- mutants partially rescues these structures. However, injection of each of the three SHFM variants fails to rescue the skeletal defects. Loss of prdm1a leads to a decreased expression of important craniofacial genes, such as dlx5a/dlx6a, hand2, sox9b, col2a1a, and hoxb genes. ConclusionThese data suggest that the three SHFM variants are not functional and may have led to the craniofacial defects observed in the humans. Finally, they demonstrate how Prdm1a can directly bind and regulate craniofacial gene expression.

developmental biology↗

bioRxiv2019

The conserved and divergent roles of Prdm3 and Prdm16 in zebrafish and mouse craniofacial development

The formation of the craniofacial skeleton is a highly dynamic process that requires proper orchestration of various cellular processes in cranial neural crest cell (cNCC) development, including cell migration, proliferation, differentiation, polarity and cell death. Alterations that occur during cNCC development result in congenital birth defects and craniofacial abnormalities such as cleft lip with or without cleft palate. While the gene regulatory networks facilitating neural crest development have been extensively studied, the epigenetic mechanisms by which these pathways are activated or repressed in a temporal and spatially regulated manner remain largely unknown. Chromatin modifers can precisely modify gene expression through a variety of mechanisms including histone modifications such as methylation. Here, we investigated the role of two members of the PRDM (Positive regulatory domain) histone methyltransferase family, Prdm3 and Prdm16 in craniofacial development using genetic models in zebrafish and mice. Loss of prdm3 or prdm16 in zebrafish causes craniofacial defects including hypoplasia of the craniofacial cartilage elements, undefined posterior ceratobranchials, and decreased mineralization of the parasphenoid. In mice, while conditional loss of Prdm3 in the early embryo proper causes mid-gestation lethality, loss of Prdm16 caused craniofacial defects including anterior mandibular hypoplasia, clefting in the secondary palate and severe middle ear defects. In zebrafish, prdm3 and prdm16 compensate for each other as well as a third Prdm family member, prdm1a. Combinatorial loss of prdm1a, prdm3, and prdm16 alleles results in severe hypoplasia of the anterior cartilage elements, abnormal formation of the jaw joint, complete loss of the posterior ceratobranchials, and clefting of the ethmoid plate. We further determined that loss of prdm3 and prdm16 reduces methylation of histone 3 lysine 9 (repression) and histone 3 lysine 4 (activation) in zebrafish. In mice, loss of Prdm16 significantly decreased histone 3 lysine 9 methylation in the palatal shelves but surprisingly did not change histone 3 lysine 4 methylation. Taken together, Prdm3 and Prdm16 play an important role in craniofacial development by maintaining temporal and spatial regulation of gene regulatory networks necessary for proper cNCC development and these functions are both conserved and divergent across vertebrates.

developmental biology↗

bioRxiv2016

The genome-wide transcriptional response to varying RpoS levels in Escherichia coli K-12

The alternative sigma factor RpoS is a central regulator of a many stress responses in Escherichia coli. The level of functional RpoS differs depending on the stress. The effect of these differing concentrations of RpoS on global transcriptional responses remains unclear. We investigated the effect of RpoS concentration on the transcriptome during stationary phase in rich media. We show that 23% of genes in the E. coli genome are regulated by RpoS level, and we identify many RpoS-transcribed genes and promoters. We observe three distinct classes of response to RpoS by genes in the regulon: genes whose expression changes linearly with increasing RpoS level, genes whose expression changes dramatically with the production of only a little RpoS (\"sensitive\" genes), and genes whose expression changes very little with the production of a little RpoS (\"insensitive\"). We show that sequences outside the core promoter region determine whether a RpoS-regulated gene in sensitive or insensitive. Moreover, we show that sensitive and insensitive genes are enriched for specific functional classes, and that the sensitivity of a gene to RpoS corresponds to the timing of induction as cells enter stationary phase. Thus, promoter sensitivity to RpoS is a mechanism to coordinate specific cellular processes with growth phase, and may also contribute to the diversity of stress responses directed by RpoS.\n\nImportanceThe sigma factor RpoS is a global regulator that controls the response to many stresses in Escherichia coli. Different stresses result in different levels of RpoS production, but the consequences of this variation are unknown. We describe how changing the level of RpoS does not influence all RpoS-regulated genes equally. The cause of this variation is likely the action of transcription factors that bind the promoters of the genes. We show that the sensitivity of a gene to RpoS levels explains the timing of expression as cells enter stationary phase, and that genes with different RpoS sensitivities are enriched for specific functional groups. Thus, promoter sensitivity to RpoS is a mechanism to coordinate specific cellular processes in response to stresses.

microbiology↗