A Review of Orofacial Clefting and Current Genetic Mouse Models

The prevalence of orofacial clefts (OFCs) is nearly 10.2 per 10,000 births in the United States and 9.9 per 10,000 births worldwide. OFCs occur as a result of a break (nonfusion) of orofacial structures during development. This can occur due to a variety of reasons;prenatal exposure to many drugs and environmental factors as well as genetic factors which are implicated in the development of OFCs. While approximately 15 types of clefts have been identified, there are at least four distinct classifications of OFCs. These include complete cleft palate with cleft lip; cleft of the anterior palate, which may/may not involve cleft lip; cleft of the posterior palate; and submucosal cleft. A number of candidate genes have been identified, including transforming growth factor beta (TGFβ) and homeobox genes (e.g., MSX1), among many others. What follows is a review of mouse models currently used in research and the classification of their overall contribution to known OFCs

Neural crest contribution to lingual mesenchyme, epithelium and developing taste papillae and taste buds

AbstractThe epithelium of mammalian tongue hosts most of the taste buds that transduce gustatory stimuli into neural signals. In the field of taste biology, taste bud cells have been described as arising from “local epithelium”, in distinction from many other receptor organs that are derived from neurogenic ectoderm including neural crest (NC). In fact, contribution of NC to both epithelium and mesenchyme in the developing tongue is not fully understood. In the present study we used two independent, well-characterized mouse lines, Wnt1-Cre and P0-Cre that express Cre recombinase in a NC-specific manner, in combination with two Cre reporter mouse lines, R26R and ZEG, and demonstrate a contribution of NC-derived cells to both tongue mesenchyme and epithelium including taste papillae and taste buds. In tongue mesenchyme, distribution of NC-derived cells is in close association with taste papillae. In tongue epithelium, labeled cells are observed in an initial scattered distribution and progress to a clustered pattern between papillae, and within papillae and early taste buds. This provides evidence for a contribution of NC to lingual epithelium. Together with previous reports for the origin of taste bud cells from local epithelium in postnatal mouse, we propose that NC cells migrate into and reside in the epithelium of the tongue primordium at an early embryonic stage, acquire epithelial cell phenotypes, and undergo cell proliferation and differentiation that is involved in the development of taste papillae and taste buds. Our findings lead to a new concept about derivation of taste bud cells that include a NC origin

BMP4-BMPR1A Signaling in β Cells Is Required for and Augments Glucose-Stimulated Insulin Secretion

SummaryImpaired glucose-stimulated insulin secretion (GSIS) and perturbed proinsulin processing are hallmarks of β cell dysfunction in type 2 diabetes. Signals that can preserve and/or enhance β cell function are therefore of great therapeutic interest. Here we show that bone morphogenetic protein 4 (Bmp4) and its high-affinity receptor, Bmpr1a, are expressed in β cells. Mice with attenuated BMPR1A signaling in β cells show decreased expression of key genes involved in insulin gene expression, proinsulin processing, glucose sensing, secretion stimulus coupling, incretin signaling, and insulin exocytosis and develop diabetes due to impaired insulin secretion. We also show that transgenic expression of Bmp4 in β cells enhances GSIS and glucose clearance and that systemic administration of BMP4 protein to adult mice significantly stimulates GSIS and ameliorates glucose tolerance in a mouse model of glucose intolerance. Thus, BMP4-BMPR1A signaling in β cells plays a key role in GSIS

BMP receptor IA is required in the mammalian embryo for endodermal morphogenesis and ectodermal patterning

AbstractBMPRIA is a receptor for bone morphogenetic proteins with high affinity for BMP2 and BMP4. Mouse embryos lacking Bmpr1a fail to gastrulate, complicating studies on the requirements for BMP signaling in germ layer development. Recent work shows that BMP4 produced in extraembryonic tissues initiates gastrulation. Here we use a conditional allele of Bmpr1a to remove BMPRIA only in the epiblast, which gives rise to all embryonic tissues. Resulting embryos are mosaics composed primarily of cells homozygous null for Bmpr1a, interspersed with heterozygous cells. Although mesoderm and endoderm do not form in Bmpr1a null embryos, these tissues are present in the mosaics and are populated with mutant cells. Thus, BMPRIA signaling in the epiblast does not restrict cells to or from any of the germ layers. Cells lacking Bmpr1a also contribute to surface ectoderm; however, from the hindbrain forward, little surface ectoderm forms and the forebrain is enlarged and convoluted. Prechordal plate, early definitive endoderm, and anterior visceral endoderm appear to be expanded, likely due to defective morphogenesis. These data suggest that the enlarged forebrain is caused in part by increased exposure of the ectoderm to signaling sources that promote anterior neural fate. Our results reveal critical roles for BMP signaling in endodermal morphogenesis and ectodermal patterning

BMP Signaling Mediated by BMPR1A in Osteoclasts Negatively Regulates Osteoblast Mineralization Through Suppression of Cx43

Osteoblasts and osteoclasts are well orchestrated through different mechanisms of communication during bone remodeling. Previously, we found that osteoclast‐specific disruption of one of the BMP receptors, Bmpr1a, results in increased osteoblastic bone formation in mice. We hypothesized that BMPR1A signaling in osteoclasts regulates production of either membrane bound proteins or secreted molecules that regulated osteoblast differentiation. In our current study, we co‐cultured wild‐type osteoblasts with either control osteoclasts or osteoclasts lacking BMPR1A signaling activity. We found that loss of Bmpr1a in osteoclasts promoted osteoblast mineralization in vitro. Further, we found that the expression of Cx43/Gja1 in the mutant osteoclasts was increased, which encoded for one of the gap junction proteins connexin 43/gap junction alpha 1. Knockdown of Gja1 in the mutant osteoclasts for Bmpr1a reduced osteoblastic mineralization when co‐cultured. Our findings suggest that GJA1 may be one of the downstream targets of BMPR1A signaling in osteoclasts that mediates osteoclast–osteoblast communication during bone remodeling. J. Cell. Biochem. 118: 605–614, 2017. © 2016 Wiley Periodicals, Inc.Disruption of Bmpr1a in osteoclasts promoted osteoblast mineralization when co‐cultured. Up‐regulation of gap junction Cx43/Gja1 in mutant osteoclasts is responsible for the enhanced osteoblast function.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135668/1/jcb25746_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135668/2/jcb25746.pd

The noncanonical BMP signaling pathway plays an important role in club cell regeneration

The bronchiole is a major site for the development of several life‐threatening disorders, including chronic obstructive pulmonary disease and lung adenocarcinomas. The bronchiolar epithelium is composed of club cells and ciliated epithelial cells, with club cells serving as progenitor cells. Presently, the identity of the cells involved in regeneration of bronchiolar epithelium and the underlying mechanisms remain incompletely understood. Here, we show that Prrx1, a homeobox transcription factor, can mark club cells in adult mice during homeostasis and regeneration. We further show that the noncanonical signaling pathway of BMPs, BMPR1A‐Tak1‐p38MAPK, plays a critical role in club cell regeneration. Ablation of Bmpr1a, Tak1, or Mapk14 (encoding p38α) in Prrx1+ club cells caused minimal effect on bronchiolar epithelium homeostasis, yet it resulted in severe defects in club cell regeneration and bronchiole repair in adult mice. We further show that this pathway supports proliferation and expansion of the regenerating club cells. Our findings thus identify a marker for club cells and reveal a critical role for the BMP noncanonical pathway in club cell regeneration.Schematic representation of our results showing the critical roles of the noncanonical signaling pathway of BMPs, (BMPR1A‐Tak1‐p38MAPK) in club cell regeneration. Naphthalene (NA) is metabolized by CYP‐2F2, which is expressed exclusively in club cells, generating cytotoxic epoxide that kills the club cells within 1.5 days after NA exposure. Under normal conditions, hyperplastic growth occurs at day 3 and the bronchiolar epithelium is restored at day 7. We show that ablation of Bmpr1a, Tak1, or Mapk14 (encoding p38α) in club cells resulted in severe defects in regeneration and bronchiole repair in adult mice.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154263/1/stem3125_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154263/2/stem3125.pd

Male germline recombination of a conditional allele by the widely used Dermo1â cre (Twist2â cre) transgene

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138422/1/dvg23048_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138422/2/dvg23048.pd

Two visual pigments in a single photoreceptor cell: Identification and histological localization of three mRNAs encoding visual pigment opsins in the retina of the butterfly Papilio xuthus

This paper describes the localization of newly identified visual pigment opsins in the tiered retina of the Japanese yellow swallowtail Papilio xuthus. We first cloned three cDNAs encoding visual pigment opsins, PxRh1, PxRh2 and PxRh3, and then carried out histological in situ hybridization to localize their mRNAs in the retina. By combining the present data with our previous electrophysiological results, we concluded that both PxRh1 and PxRh2 correspond to visual pigments expressed in photoreceptor cells sensitive in the green wavelength region (green receptors), whereas PxRh3 corresponds to a pigment in red receptors. The in situ hybridization studies showed that some photoreceptor cells express two opsin mRNAs. In the ventral half of the eye, all green receptors in the distal tier were labelled by both PxRh1 and PxRh2 probes. The labelling by the PxRh2 and PxRh3 probes was detected throughout the eye in the proximal tier; in 18 % of ommatidia, the probes labelled the same photoreceptor cell. These results suggest that the possible co-localization of two different visual pigments will broaden the sensitivity spectrum of the photoreceptor cells

Increased activity of mesenchymal ALK2â BMP signaling causes posteriorly truncated microglossia and disorganization of lingual tissues

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153778/1/dvg23337.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153778/2/dvg23337_am.pd

Conditional deletion of Bmpr1a in differentiated osteoclasts increases osteoblastic bone formation, increasing volume of remodeling bone in mice

Bone undergoes remodeling consisting of osteoclastic bone resorption followed by osteoblastic bone formation throughout life. Although the effects of bone morphogenetic protein (BMP) signals on osteoblasts have been studied extensively, the function of BMP signals in osteoclasts has not been fully elucidated. To delineate the function of BMP signals in osteoclasts during bone remodeling, we deleted BMP receptor type IA ( Bmpr1a ) in an osteoclast‐specific manner using a knock‐in Cre mouse line to the cathepsin K locus ( Ctsk Cre/+ ;Bmpr1a flox/flox , designated as Bmpr1a ΔOc/ΔOc ). Cre was specifically expressed in multinucleated osteoclasts in vivo. Cre‐dependent deletion of the Bmpr1a gene occurred at 4 days after cultivation of bone marrow macrophages obtained from Bmpr1a ΔOc/ΔOc with RANKL. These results suggested that Bmpr1a was deleted after formation of osteoclasts in Bmpr1a ΔOc/ΔOc mice. Expression of bone‐resorption markers increased, thus suggesting that BMPRIA signaling negatively regulates osteoclast differentiation. Trabeculae in tibia and femurs were thickened in 3.5‐, 8‐, and 12‐week‐old Bmpr1a ΔOc/ΔOc mice. Bone histomorphometry revealed increased bone volume associated with increased osteoblastic bone‐formation rates (BFR) in the remodeling bone of the secondary spongiosa in Bmpr1a ΔOc/ΔOc tibias at 8 weeks of age. For comparison, we also induced an osteoblast‐specific deletion of Bmpr1a using Col1a1‐Cre. The resulting mice showed increased bone volume with marked decreases in BFR in tibias at 8 weeks of age. These results indicate that deletion of Bmpr1a in differentiated osteoclasts increases osteoblastic bone formation, thus suggesting that BMPR1A signaling in osteoclasts regulates coupling to osteoblasts by reducing bone‐formation activity during bone remodeling. © 2011 American Society for Bone and Mineral ResearchPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87086/1/477_ftp.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/87086/2/jbmr_477_sm_SupplData.pd