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Biomedical subjects

Michael Weinstein

Publications and source records attributed to Michael Weinstein.

At least 19 recordsLinked to original sources
PubMed2006

TGIF inhibits retinoid signaling.

TGIF (TG-interacting factor) represses transforming growth factor beta (TGF-beta)-activated gene expression and can repress transcription via a specific retinoid response element. Mutations in human TGIF are associated with holoprosencephaly, a severe defect of craniofacial development with both genetic and environmental causes. Both TGF-beta and retinoic acid signaling are implicated in craniofacial development. Here, we analyze the role of TGIF in regulating retinoid responsive gene expression. We demonstrate that TGIF interacts with the ligand binding domain of the RXRalpha retinoid receptor and represses transcription from retinoid response elements. TGIF recruits the general corepressor, CtBP, to RXRalpha, and this recruitment is required for full repression by TGIF. Interaction between TGIF and RXRalpha is reduced by the addition of retinoic acid, consistent with a role for TGIF as an RXRalpha transcriptional corepressor. We created a Tgif null mutation in mice and tested the sensitivity of mutant mice to increased levels of retinoic acid. Tgif mutant embryos are more sensitive to retinoic acid-induced teratogenesis, and retinoid target genes are expressed at a higher level in tissues from Tgif null mice. These results demonstrate an important role for TGIF as a transcriptional corepressor, which regulates developmental signaling by retinoic acid, and raises the possibility that TGIF may repress other RXR-dependent transcriptional responses.

Animals↗
PubMed2005

CDG-IL: an infant with a novel mutation in the ALG9 gene and additional phenotypic features.

We describe the second case of congenital disorder of glycosylation type IL (CDG-IL) caused by deficiency of the ALG9 a1,2 mannosyltransferase enzyme. The female infant's features included psychomotor retardation, seizures, hypotonia, diffuse brain atrophy with delayed myelination, failure to thrive, pericardial effusion, cystic renal disease, hepatosplenomegaly, esotropia, and inverted nipples. Lipodystrophy and dysmorphic facial features were absent. Magnetic resonance imaging of the brain showed volume loss in the cerebral hemispheres and cerebellum and delayed myelination. Laboratory investigations revealed low levels of multiple serum proteins including antithrombin III, factor XI, and cholesterol. Hypoglycosylation was confirmed by the typical CDG type 1 pattern of serum transferrin analyzed by isoelectric focusing. A defect in the ALG9 enzyme was suggested by the accumulation of the DolPP-GlcNAc2Man6 and DolPP-GlcNAc2Man8 in the patient's fibroblasts and confirmed by mutation analysis: the patient is homozygous for the ALG9 mutation p.Y286C. The causal effect of the mutation was shown by complementation assays in alg9 deficient yeast cells. The child described here further delineates the clinical spectrum of CDG-IL and confirms the significant clinical overlap amongst CDG subtypes.

Cathepsin A↗
PubMed2005

Baalc, a marker of mesoderm and muscle.

Transcripts of the Brain and Acute Leukemia, Cytoplasmic (BAALC) gene are expressed in human neuroectodermal tissues and in CD34-positive bone marrow cells. High transcript levels occur in leukemic blasts from some patients with acute myeloid leukemia (AML), where high expression is an independent marker of poor prognosis. To gain insight into the hitherto unknown function of BAALC/Baalc, we studied its protein expression in embryonic and adult mouse tissue by immunohistochemical analysis. Baalc protein was mainly expressed in developing and mature muscle cells (cardiac, skeletal, and smooth) beginning on day E9 (heart). Signal was seen in the pre-muscle mesodermal cells of the dermatomyotome regions, and the derivatives of the lateral plate and intermediate mesoderm such as smooth muscle wall of the esophagus, stomach, the gut tube, bronchi, small blood vessels, and urinary bladder. This pattern continued through the late embryonic stages into adulthood. Baalc appeared to localize in the cytoplasm, adjacent to the cell membrane. This is distinctly observed in adult skeletal muscle cells. Baalc co-localized with known muscle-associated proteins but not with neural crest or neuronal markers. Scattered expression in adult bone marrow hematopoietic cells and weak expression in the brain neuropil also occurred. In conclusion, BAALC/Baalc is a marker of the mesodermal lineage, especially muscle.

Animals↗
PubMed2005

Smad1 and Smad8 function similarly in mammalian central nervous system development.

Smads 1, 5, and 8 are the intracellular mediators for the bone morphogenetic proteins (BMPs), which play crucial roles during mammalian development. Previous research has shown that Smad1 is important in the formation of the allantois, while Smad5 has been shown to be critical in the process of angiogenesis. To further analyze the BMP-responsive Smads, we disrupted the murine Smad8 gene utilizing the Cre/loxP system. A Smad8 hypomorphic allele (Smad8(Deltaexon3)) was constructed that contains an in-frame deletion of exon 3, removing one-third of the MH2 domain and a small portion of the linker region. Xenopus injection assays indicated that this Smad8 deletion allele is still functional but has reduced ventralizing capability compared to the wild type. Although Smad8(Deltaexon3/Deltaexon3) embryos are phenotypically normal, homozygotes of another hypomorphic allele of Smad8 (Smad8(3loxP)) containing a neomycin cassette within intron 3, phenocopy an embryonic brain defect observed in roughly 22% of Smad1(+/)(-) embryos analyzed at embryonic day 11.5. These observations suggest that BMP-responsive Smads have critical functions in the development of the mammalian central nervous system.

Alleles↗
PubMed2004

Smad2 and Smad3 coordinately regulate craniofacial and endodermal development.

Ligands of the transforming growth factor-beta (TGF-beta) superfamily are involved in numerous developmental and disease processes. TGF-beta, activins, and nodal ligands operate through the highly homologous Smad2 and Smad3 intracellular mediators. Smad2 mutants exhibit early embryonic lethality, while Smad3 mutants are viable, but show a plethora of postnatal phenotypes, including immune dysfunction and skeletal abnormalities. Previously, we have shown that the Smad2 and Smad3 genes function cooperatively during liver morphogenesis. Here we show that Smad2 and Smad3 are required at a full dosage for normal embryonic development. Animals lacking one allele of each gene exhibit a variably penetrant phenotype in which structures in the anterior and ventral midline are reduced or lost; additionally, we demonstrate that this craniofacial defect and the previously reported hepatic phenotypes are both due to defects in the definitive endoderm. A reduction of endodermal gene expression as well as a failure to displace the visceral endoderm occurs despite the formation of a normal foregut pocket. This precedes any defects in anterior patterning and likely causes the abnormalities observed in craniofacial and midline development, as well as hepatogenesis.

Animals↗
PubMed2004

The inositol 3-phosphatase PTEN negatively regulates Fc gamma receptor signaling, but supports Toll-like receptor 4 signaling in murine peritoneal macrophages.

Fc gamma R clustering in macrophages activates signaling events that result in phagocytosis. Phagocytosis is accompanied by the generation harmful byproducts such as reactive oxygen radicals and production of inflammatory cytokines, which mandate that the phagocytic process be subject to a tight regulation. The molecular mechanisms involved in this regulation are not fully understood. In this study, we have examined the role of the inositol 3-phosphatase and tensin homologue deleted on chromosome 10 (PTEN) in Fc gamma R-induced macrophage function. We demonstrate that in ex vivo murine peritoneal macrophages that are deficient in PTEN expression, Fc gamma R-induced Akt and extracellular signal-regulated kinase phosphorylation are enhanced. Notably, PTEN(-/-) macrophages showed constitutively high phosphorylation of Akt. However, PTEN did not seem to influence tyrosine phosphorylation events induced by Fc gamma R clustering. Furthermore, PTEN(-/-) macrophages displayed enhanced phagocytic ability. Likewise, Fc gamma R-induced production of TNF-alpha, IL-6, and IL-10 was significantly elevated in PTEN(-/-) macrophages. Surprisingly, LPS-induced TNF-alpha production was down-regulated in PTEN(-/-) macrophages. Analyzing the molecular events leading to PTEN influence on LPS/Toll-like receptor 4 (TLR4) signaling, we found that LPS-induced activation of mitogen-activated protein kinases is suppressed in PTEN(-/-) cells. Previous reports indicated that LPS-induced mitogen-activated protein kinase activation is down-regulated by phosphatidylinositol 3-kinase through the activation of Akt. Our observation that Akt activation is basally enhanced in PTEN(-/-) cells suggests that PTEN supports TLR4-induced inflammatory responses by suppressing the activation of Akt. Thus, we conclude that PTEN is a negative regulator of Fc gamma R signaling, but a positive regulator of TLR4 signaling. These findings are the first to demonstrate a role for PTEN in Fc gamma R- and TLR4-mediated macrophage inflammatory response.

Animals↗
PubMed2004

Generation of novel conditional and hypomorphic alleles of the Smad2 gene.

Smad2 is an intracellular mediator of the transforming growth factor beta signaling (TGFbeta) pathway. It has been previously shown that, in the mouse, ablation of functional Smad2 results in embryonic lethality due to gastrulation defects. To circumvent the early lethality and study the spatially and temporally specific functions of Smad2, we utilized the Cre-loxP system to generate a Smad2 conditional allele. Here we show that a conditional allele, Smad2(flox), was generated. In this allele, exons 9 and 10 are flanked by loxP sites and the gene is functionally wildtype. Cre-mediated recombination results in a deletion allele which phenocopies our previously reported Smad2(DeltaC) null mutation. To generate this conditional allele, we first made a targeted mutation which introduced a floxed neo cassette into intron 10. This allele (Smad2(3loxP)) functions hypomorphically when placed opposite a null allele, and unlike the other published Smad2 hypomorphic allele, can be maintained in the homozygous state.

Alleles↗
PubMed2004

Effectiveness and safety of tissue plasminogen activator in the management of complicated parapneumonic effusions.

OBJECTIVE: The management of parapneumonic effusions in children is controversial. The objective of this study was to evaluate the effectiveness and safety of intrapleural tissue plasminogen activator (tPA) in children who require tube thoracostomy for drainage of a complicated parapneumonic effusion. METHODS: An observational cohort study was used to compare children who were treated with intrapleural tPA (either early or late administration) with children who were treated with thoracostomy tube drainage alone. RESULTS: Over a 6-year period, 12 children received early tPA (within 24 hours of diagnosis), 18 children received late tPA (>24 hours after diagnosis), and 23 children received thoracostomy tube drainage alone for the management of a complicated parapneumonic effusion. Total pleural fluid drainage was highest for the late tPA group (691 mL vs 360 mL in the control group); however, the rate of pleural fluid drainage was highest for the early tPA group (7 mL/h vs 3 mL/h in the control group). The duration of chest tube placement was 84 hours for the early tPA group, 209 hours for the late tPA group, and 130 hours for the control group. There was a significant difference in duration of chest tube placement between the early and late tPA groups. No child who was treated with tPA developed local or systemic bleeding. CONCLUSIONS: Early administration of intrapleural tPA seems to be a safe and potentially effective treatment in children with complicated parapneumonic effusions. Randomized controlled trial evidence is needed to confirm this finding.

Chest Tubes↗
PubMed2003

Rb function in extraembryonic lineages suppresses apoptosis in the CNS of Rb-deficient mice.

Retinoblastoma (Rb)-deficient embryos show severe defects in neurogenesis, erythropoiesis, and lens development and die at embryonic day 14.5. Our recent results demonstrated a drastic disorganization of the labyrinth layer in the placenta of Rb-deficient embryos, accompanied by reduced placental transport function. When these Rb-/- embryos were supplied with a wild-type placenta by using either tetraploid aggregation or genetic approaches, animals survived until birth. Here we analyze the role of extraembryonic Rb in regulating proliferation, apoptosis, and differentiation in the rescued animals at different developmental stages. Many of the neurological and erythroid abnormalities thought to be responsible for the embryonic lethality of Rb-/- animals, including the ectopic apoptosis in the CNS, were virtually absent in rescued Rb-/- pups. However, rescued animals died at birth with severe skeletal muscle defects. Like in Rb knockout embryos, rescued animals showed a marked increase in DNA replication and cell division in the CNS. In sharp contrast, the typical widespread neuronal apoptosis was absent in Rb-deficient embryos reconstituted with a normal placenta. In lens fiber cells, however, the inappropriate proliferation and apoptosis that is normally observed in Rb-/- embryos continued unabated in rescued animals. These results demonstrate that Rb function in extraembryonic lineages plays an important role in the survival of neuronal cells and in the differentiation of the erythroid lineage, providing mechanistic insight into the cell autonomous and nonautonomous functions of Rb during development.

Animals↗
PubMed2003

Extra-embryonic function of Rb is essential for embryonic development and viability.

The retinoblastoma (Rb) gene was the first tumour suppressor identified. Inactivation of Rb in mice results in unscheduled cell proliferation, apoptosis and widespread developmental defects, leading to embryonic death by day 14.5 (refs 2-4). However, the actual cause of the embryonic lethality has not been fully investigated. Here we show that loss of Rb leads to excessive proliferation of trophoblast cells and a severe disruption of the normal labyrinth architecture in the placenta. This is accompanied by a decrease in vascularization and a reduction in placental transport function. We used two complementary techniques-tetraploid aggregation and conditional knockout strategies-to demonstrate that Rb-deficient embryos supplied with a wild-type placenta can be carried to term, but die soon after birth. Most of the neurological and erythroid abnormalities thought to be responsible for the embryonic lethality of Rb-null animals were virtually absent in rescued Rb-null pups. These findings identify and define a key function of Rb in extra-embryonic cell lineages that is required for embryonic development and viability, and provide a mechanism for the cell autonomous versus non-cell autonomous roles of Rb in development.

Animals↗
PubMed2003

Pemphigus vulgaris: the eyes have it.

Pemphigus vulgaris is a potentially fatal autoimmune blistering disease that is rare in childhood. We report 2 recent cases seen contemporaneously in adolescents who presented with chronic oral mucosal lesions and conjunctivitis. The previously unemphasized ocular manifestations are described and the importance of a biopsy in establishing the diagnosis in instances of unexplained chronic mucositis is stressed.

Adolescent↗