Biosintese van 'n afwykende vorm van tipe I prokollageen in 'n familie met osteogenesis imperfecta

MSc (Biochemie), North-West University, Potchefstroom CampusBIOSYNTHESIS OF AN ABNORMAL TYPE I PROCOLLAGEN IN A FAMILY WITH OSTEOGENESIS IMPERFECTA (Original title: Biosintese van 'n afwykende vorm van tipe I prokollageen in 'n familie met osteogenesis imperfecta). Osteogenesis imperfecta (01) is a heterogeneous group of heritable disorders of connective tissue which are characterized by increased fragility of bone and are frequently associated with other clinical features, such as skeletal deformities, blue sclerae, hearing impairment and dentinogenesis imperfecta. 01 can be divided into at least four different subtypes : type I, type II, type III and type IV. A variety of observations, made on cultured skin fibroblasts, showed that some forms of the heritable disorders of connective tissues involve changes in the metabolism of type I procollagen. Synthesis of procollagen was examined in skin fibroblasts from a patient with type IOI. Treatment of the procollagen with pepsin, followed by SOS-PAGE, revealed the presence of type I collagen in which two al (I) chains were linked through interchain disulfide bonds. Fragmentation of the disulfide bonded al (I) dimers with vertebrate collagenase and cyanogen bromide,demonstrated the presence of a cysteine residue in al (I)CBS, a fragment containing amino acid residues 124 - 402 of the a l (I) collagen chain. The presence of one mutant pro a l (I) chain in trimers of type I procollagen was found to reduce the thermal stability of the protein with 2,5~ C. In contrast , the presence of two mutant proal(I) chains was found to reduce the thermal stability of type I procollagen with 1°c. Three kinds of type I trimers were therefore formed: a normal type with normal proa l(I) chains; a type I trimer with one normal and one mutant proa l(I) chain and a type I trimer with two mutant proal(I) chains. Type I trimers containing one mutant proa l (I) chain were secreted at a slower rate than normal . A fraction of 63% was secreted in the fast phase of secretion as opposed to the normal fraction of 96 %. The presence of the mutant proa l(I) chains in type I trimers had ·no adverse effect on processing by N-proteinase. The most likely explanation for these disruptive changes in the physical stability and secretion of the mutant procollagen is that a cysteine res i due is substituted for a glycine in half of the proa l(I) chains synthesized by the patient's fibroblasts. Radiolo gica l examination of the proband and seven other family members, representing three generations of a large pedigree , revealed a large variation in phenotype . Analysis of the collagen from fibroblasts of less and more severely affected members, all showed the presence of the cysteine containing proal( I ) chains.Master

β-catenin-mediated adhesion is required for successful preimplantation mouse embryo development.

β-catenin (CTNNB1) is integral to cell adhesion and to the canonical Wnt signaling pathway. The effects of maternal and zygotic CTNNB1 on embryogenesis have each been separately assessed, whereas the effect of its total absence has not. As the \u27traditional\u27 conditional Ctnnb1 knockout alleles give rise to truncated CTNNB1 fragments, we designed a new knockout allele incapable of CTNNB1 production. Mouse embryos lacking intact maternal/zygotic CTNNB1 from two knockout strains were examined in detail. Preimplantation embryos are formed, yet abnormalities in their size and shape were found throughout pre- and early postimplantation development. In the absence of the zona pellucida, embryos lacking CTNNB1 undergo fission and these separated blastomeres can become small trophoblastic vesicles, which in turn induce decidual reactions. Comparing the severity of this defective adhesion phenotype in embryos bearing the null allele with those carrying the \u27traditional\u27 knockout allele suggests a hypomorphic effect of the truncated CTNNB1 protein fragment, an important observation with possible impact on previous and future studies. Development 2016 Jun 1; 143(11):1993-

Polymer-based miniature flexible capacitive pressure sensor for intraocular pressure (IOP) monitoring inside a mouse eye.

This paper presents an ultra-thin and flexible polymer-based capacitive pressure sensor for intraocular pressure (IOP) monitoring in a mouse eye. Due to the size limitation of the anterior chamber in the mouse eye, a volume of approximately 700 × 700 × 150 μm(3) on a small substrate is available for the MEMS capacitive pressure sensor. Moreover, the sensor would ideally be easily injectable into place. Further complicating the sensing is the need to operate the device on the curved surface of the anterior chamber with minimum damage to the eye tissue. Therefore, a thin and flexible substrate is required. We fabricate sensors by exploiting Parylene as a biocompatible structural material in a suitable form factor and 25 μm thick liquid crystal polymer (LCP) as a soft and flexible host substrate. Using our approach, the flexibility and small form factor necessary for a mouse eye implant is achieved, along with the sensitivity required to monitor IOP fluctuations. This device will allow better study of glaucoma through close monitoring in mice after integration with other components

Trim28 is required for epigenetic stability during mouse oocyte to embryo transition.

Phenotypic variability in genetic disease is usually attributed to genetic background variation or environmental influence. Here, we show that deletion of a single gene, Trim28 (Kap1 or Tif1β), from the maternal germ line alone, on an otherwise identical genetic background, results in severe phenotypic and epigenetic variability that leads to embryonic lethality. We identify early and minute epigenetic variations in blastomeres of the preimplantation embryo of these animals, suggesting that the embryonic lethality may result from the misregulation of genomic imprinting in mice lacking maternal Trim28. Our results reveal the long-range effects of a maternal gene deletion on epigenetic memory and illustrate the delicate equilibrium of maternal and zygotic factors during nuclear reprogramming

Chronic consumption of a western diet induces robust glial activation in aging mice and in a mouse model of Alzheimer\u27s disease.

Studies have assessed individual components of a western diet, but no study has assessed the long-term, cumulative effects of a western diet on aging and Alzheimer\u27s disease (AD). Therefore, we have formulated the first western-style diet that mimics the fat, carbohydrate, protein, vitamin and mineral levels of western diets. This diet was fed to aging C57BL/6J (B6) mice to identify phenotypes that may increase susceptibility to AD, and to APP/PS1 mice, a mouse model of AD, to determine the effects of the diet in AD. Astrocytosis and microglia/monocyte activation were dramatically increased in response to diet and was further increased in APP/PS1 mice fed the western diet. This increase in glial responses was associated with increased plaque burden in the hippocampus. Interestingly, given recent studies highlighting the importance of TREM2 in microglia/monocytes in AD susceptibility and progression, B6 and APP/PS1 mice fed the western diet showed significant increases TREM2+ microglia/monocytes. Therefore, an increase in TREM2+ microglia/monocytes may underlie the increased risk from a western diet to age-related neurodegenerative diseases such as Alzheimer\u27s disease. This study lays the foundation to fully investigate the impact of a western diet on glial responses in aging and Alzheimer\u27s disease. Sci Rep 2016 Feb 18; 6:21568

Chronic consumption of a western diet induces robust glial activation in aging mice and in a mouse model of Alzheimer’s disease

Studies have assessed individual components of a western diet, but no study has assessed the long-term, cumulative effects of a western diet on aging and Alzheimer’s disease (AD). Therefore, we have formulated the first western-style diet that mimics the fat, carbohydrate, protein, vitamin and mineral levels of western diets. This diet was fed to aging C57BL/6J (B6) mice to identify phenotypes that may increase susceptibility to AD, and to APP/PS1 mice, a mouse model of AD, to determine the effects of the diet in AD. Astrocytosis and microglia/monocyte activation were dramatically increased in response to diet and was further increased in APP/PS1 mice fed the western diet. This increase in glial responses was associated with increased plaque burden in the hippocampus. Interestingly, given recent studies highlighting the importance of TREM2 in microglia/monocytes in AD susceptibility and progression, B6 and APP/PS1 mice fed the western diet showed significant increases TREM2+ microglia/monocytes. Therefore, an increase in TREM2+ microglia/monocytes may underlie the increased risk from a western diet to age-related neurodegenerative diseases such as Alzheimer’s disease. This study lays the foundation to fully investigate the impact of a western diet on glial responses in aging and Alzheimer’s disease

YBR/EiJ mice: a new model of glaucoma caused by genes on chromosomes 4 and 17.

A variety of inherited animal models with different genetic causes and distinct genetic backgrounds are needed to help dissect the complex genetic etiology of glaucoma. The scarcity of such animal models has hampered progress in glaucoma research. Here, we introduce a new inherited glaucoma model: the inbred mouse strain YBR/EiJ (YBR). YBR mice develop a form of pigmentary glaucoma. They exhibit a progressive age-related pigment-dispersing iris disease characterized by iris stromal atrophy. Subsequently, these mice develop elevated intraocular pressure (IOP) and glaucoma. Genetic mapping studies utilizing YBR as a glaucoma-susceptible strain and C57BL/6J as a glaucoma-resistant strain were performed to identify genetic loci responsible for the iris disease and high IOP. A recessive locus linked to Tyrp1(b) on chromosome 4 contributes to iris stromal atrophy and high IOP. However, this is not the only important locus. A recessive locus on YBR chromosome 17 causes high IOP independent of the iris stromal atrophy. In specific eyes with high IOP caused by YBR chromosome 17, the drainage angle (through which ocular fluid leaves the eye) is largely open. The YBR alleles of genes on chromosomes 4 and 17 underlie the development of high IOP and glaucoma but do so through independent mechanisms. Together, these two loci act in an additive manner to increase the susceptibility of YBR mice to the development of high IOP. The chromosome 17 locus is important not only because it causes IOP elevation in mice with largely open drainage angles but also because it exacerbates IOP elevation and glaucoma induced by pigment dispersion. Therefore, YBR mice are a valuable resource for studying the genetic etiology of IOP elevation and glaucoma, as well as for testing new treatments. Dis Model Mech 2016 Aug 9(8):863-71

Mutations in a P-Type ATPase Gene Cause Axonal Degeneration

<div><p>Neuronal loss and axonal degeneration are important pathological features of many neurodegenerative diseases. The molecular mechanisms underlying the majority of axonal degeneration conditions remain unknown. To better understand axonal degeneration, we studied a mouse mutant wabbler-lethal (<em>wl</em>). Wabbler-lethal (<em>wl</em>) mutant mice develop progressive ataxia with pronounced neurodegeneration in the central and peripheral nervous system. Previous studies have led to a debate as to whether myelinopathy or axonopathy is the primary cause of neurodegeneration observed in <em>wl</em> mice. Here we provide clear evidence that wabbler-lethal mutants develop an axonopathy, and that this axonopathy is modulated by <em>Wld^s</em> and <em>Bax</em> mutations. In addition, we have identified the gene harboring the disease-causing mutations as <em>Atp8a2</em>. We studied three <em>wl</em> alleles and found that all result from mutations in the <em>Atp8a2</em> gene. Our analysis shows that ATP8A2 possesses phosphatidylserine translocase activity and is involved in localization of phosphatidylserine to the inner leaflet of the plasma membrane. <em>Atp8a2</em> is widely expressed in the brain, spinal cord, and retina. We assessed two of the mutant alleles of <em>Atp8a2</em> and found they are both nonfunctional for the phosphatidylserine translocase activity. Thus, our data demonstrate for the first time that mutation of a mammalian phosphatidylserine translocase causes axon degeneration and neurodegenerative disease.</p> </div