Development

Maintaining tissue homeostasis depends on a balance of cell proliferation, differentiation and apoptosis. Within the epidermis the levels of the polyamines putrescine, spermidine and spermine are altered in many different skin conditions yet their role in epidermal tissue homeostasis is poorly understood. We identify the polyamine regulator, AMD1, as a crucial regulator of keratinocyte differentiation. AMD1 protein is upregulated on differentiation and highly expressed in the suprabasal layers of the human epidermis.

CRISPR-based transcriptional activation is a powerful tool for functional gene interrogation; however, delivery difficulties have limited its applications in vivo. Here, we created a mouse model expressing all components of the CRISPR-Cas9 guide RNA-directed Synergistic Activation Mediator (SAM) from a single transcript that is capable of activating target genes in a tissue-specific manner. We optimized Lipid Nanoparticles and Adeno-Associated Virus guide RNA delivery approaches to achieve expression modulation of one or more genes in vivo.

Previous studies on mouse embryo limbs have established that interzone mesenchymal progenitor cells emerging at each prescribed joint site give rise to joint tissues over fetal time. These incipient tissues undergo structural maturation and morphogenesis postnatally, but underlying mechanisms of regulation remain unknown. Hox11 genes dictate overall zeugopod musculoskeletal patterning and skeletal element identities during development.

Skeletal muscle myofibers can be separated into functionally distinct cell types that differ in gene and protein expression. Current single cell expression data is generally based upon single nucleus RNA, rather than whole myofiber material. We examined if a whole-cell flow sorting approach could be applied to perform single cell RNA-seq (scRNA-seq) in a single muscle type. We performed deep, whole cell, scRNA-seq on intact and fragmented skeletal myofibers from the mouse fast-twitch flexor digitorum brevis muscle utilizing a flow-gated method of large cell isolation.

Organs are composed of diverse cell types that traverse transient states during organogenesis. To interrogate this diversity during human development, we generate a single-cell transcriptome atlas from multiple developing endodermal organs of the respiratory and gastrointestinal tract. We illuminate cell states, transcription factors, and organ-specific epithelial stem cell and mesenchyme interactions across lineages.

Dental enamel forms extracellularly as thin ribbons of amorphous calcium phosphate (ACP) that initiate on dentin mineral in close proximity to the ameloblast distal membrane. Secreted proteins are critical for this process. Enam-/- and Ambn-/- mice fail to form enamel. We characterize enamel ribbon formation in wild-type (WT), Amelx-/- and Mmp20-/- mouse mandibular incisors using focused ion beam scanning electron microscopy (FIB-SEM) in inverted backscatter mode. In Amelx-/- mice, initial enamel mineral ribbons extending from dentin are similar in form to those of WT mice.

Osteocytes are the primary mechanosensitive cells in bone. However, their location in mineralized matrix has limited the in vivo study of osteocytic genes induced by mechanical loading. Laser Capture Microdissection (LCM) allows isolation of intracortical bone (Intra-CB), enriched for osteocytes, from bone tissue for gene expression analysis. We used microarray to analyze gene expression from mouse tibial Intra-CB dissected using LCM 4 h after a single loading bout or after 5 days of loading.

Sensory neurons within DRGs are broadly divided into three types that transmit nociceptive, mechanical, and proprioceptive signals. These subtypes are established during in utero development when sensory neurons differentiate into distinct categories according to a complex developmental plan. Most of what we know about this developmental plan comes from studies in rodents and little is known about this process in humans. The present study documents the expression of key genes involved in human sensory neuron development during the late first and early second trimesters (9-16WG).

We sought to understand how perturbation of signaling pathways and their targets generates variable phenotypes. In humans, GATA3 associates with highly variable defects, such as HDR syndrome, microsomia and choanal atresia. We previously characterized a zebrafish point mutation in gata3 with highly variable craniofacial defects to the posterior palate. This variability could be due to residual Gata3 function, however, we observe the same phenotypic variability in gata3 null mutants. Using hsp:GATA3-GFP transgenics, we demonstrate that Gata3 function is required between 24 and 30 hpf.

Zika virus (ZIKV), a mosquito-borne flavivirus, can cause severe eye disease and even blindness in newborns. However, ZIKV-induced retinal lesions have not been studied in a comprehensive way, mechanisms of ZIKV-induced retinal abnormalities are unknown, and no therapeutic intervention is available to treat or minimize the degree of vision loss in patients. Here, we developed a novel mouse model of ZIKV infection to evaluate its impact on retinal structure. ZIKV (20 plaque-forming units) was inoculated into neonatal wild type C57BL/6J mice at postnatal day (P) 0 subcutaneously.