Ventral neural tube cells differentiate into hepatocytes in the chick embryo

A population of ventral neural tube cells has recently been shown to migrate out of the hind brain neural tube via the vagus nerve and contribute to the developing gastrointestinal tract. Since liver is also innervated by the vagus nerve, we sought to determine if these cells also migrate into the liver. Ventral neural tube cells in the caudal hindbrain of chick embryos were tagged with a replication-deficient retroviral vector containing the LacZ gene on embryonic day 2. Embryos were processed for detection of labeled cells on embryonic day 5 and 11. Labeled cells were seen in the liver on both days and identified as hepatocytes. Previously, it was believed that all hepatocytes develop from the gut endoderm. Results of the present study show an additional source for the formation of liver cells. Received 25 August 1998; received after revision 5 November 1998; accepted 5 November 1998     

Polymorphism in the regulatory sequence of the human hsp70-1 gene does not affect heat shock factor binding or heat shock protein synthesis

A bi-allelic polymorphism found in the regulatory region of the human heat shock (HS) protein (HSP) hsp70-1 gene, which comprises an A-->C transversion, 3 bp upstream of the HS element (HSE), has been associated with extended HLA haplotypes. In view of the chaperoning and protective functions of Hsp70, we investigated whether this hsp70-1 bi-allelic polymorphism could modulate the stress response, which may relate to enhanced resistance or susceptibility to certain diseases. We compared the basal and HS-induced HS factor (HSF)-binding activity of the two polymorphic HSEs, hsp70-1 mRNA accumulation and HSP expression in two human Epstein Barr virus (EBV)-transformed B cell lines typed for hsp70-1 promoter alleles. Our results suggest that hsp70-1 promoter polymorphism does not influence HSF-binding activity, hsp70 mRNA accumulation or synthesis in human EBV-transformed B cell lines.     

Beyond blood pressure: new roles for angiotensin II

Since the discovery 100 years ago by Tigerstedt and Bergman of renin, an acid protease generating angiotensin peptide, numerous discoveries have advanced our understanding of the renin-angiotensin system (RAS). The recent cloning of angiotensin receptors and the availability of specific receptor ligands have allowed characterization of angiotensin-receptor-mediated actions, and an increasing number of studies using biochemical, pharmacological and molecular biological methods has focused on the many different physiological actions of the RAS in various tissues. Angiotensin II, the main effector peptide of the RAS, exerts most of its known actions in blood pressure control and body fluid homeostasis via the AT, receptor. AT, receptors not only play a role in growth control and cell differentiation but have been implicated in apoptosis and tissue regeneration. This review focuses on the extrarenal functions of angiotensin, especially in neuronal cells and the nervous system, and on recent advances in angiotensin receptor research.     

Mutations in CUBN, encoding the intrinsic factor-vitamin B12 receptor, cubilin, cause hereditary megaloblastic anaemia 1

Megaloblastic anaemia 1 (MGA1, OMIM 261100) is a rare, autosomal recessive disorder characterized by juvenile megaloblastic anaemia, as well as neurological symptoms that may be the only manifestations. At the cellular level, MGA1 is characterized by selective intestinal vitamin B12 (B12, cobalamin) malabsorption. MGA1 occurs worldwide, but its prevalence is higher in several Middle Eastern countries and Norway, and highest in Finland (0.8/100,000). We previously mapped the MGA1 locus by linkage analysis in Finnish and Norwegian families to a 6-cM region on chromosome 10p12.1 (ref. 8). A functional candidate gene encoding the intrinsic factor (IF)-B12 receptor, cubilin, was recently cloned; the human homologue, CUBN, was mapped to the same region. We have now refined the MGA1 region by linkage disequilibrium (LD) mapping, fine-mapped CUBN and identified two independent disease-specific CUBN mutations in 17 Finnish MGA1 families. Our genetic and molecular data indicate that mutations in CUBN cause MGA1.     

High-resolution mapping of quantitative trait loci in outbred mice

Screening the whole genome of a cross between two inbred animal strains has proved to be a powerful method for detecting genetic loci underlying quantitative behavioural traits, but the level of resolution offered by quantitative trait loci (QTL) mapping is still too coarse to permit molecular cloning of the genetic determinants. To achieve high-resolution mapping, we used an outbred stock of mice for which the entire genealogy is known. The heterogeneous stock (HS) was established 30 years ago from an eight-way cross of C57BL/6, BALB/c, RIII, AKR, DBA/2, I, A/J and C3H inbred mouse strains. At the time of the experiment reported here, the HS mice were at generation 58, theoretically offering at least a 30-fold increase in resolution for QTL mapping compared with a backcross or an F2 intercross. Using the HS mice we have mapped a QTL influencing a psychological trait in mice to a 0.8-cM interval on chromosome 1. This method allows simultaneous fine mapping of multiple QTLs, as shown by our report of a second QTL on chromosome 12. The high resolution possible with this approach makes QTLs accessible to positional cloning.     

Mutations in ATP2A2, encoding a Ca2+ pump, cause Darier disease

Darier disease (DD) is an autosomal-dominant skin disorder characterized by loss of adhesion between epidermal cells (acantholysis) and abnormal keratinization. Recently we constructed a 2.4-Mb, P1-derived artificial chromosome contig spanning the DD candidate region on chromosome 12q23-24.1. After screening several genes that mapped to this region, we identified mutations in the ATP2A2 gene, which encodes the sarco/endoplasmic reticulum Ca2(+)-ATPase type 2 isoform (SERCA2) and is highly expressed in keratinocytes. Thirteen mutations were identified, including frameshift deletions, in-frame deletions or insertions, splice-site mutations and non-conservative missense mutations in functional domains. Our results demonstrate that mutations in ATP2A2 cause DD and disclose a role for this pump in a Ca(2+)-signalling pathway regulating cell-to-cell adhesion and differentiation of the epidermis.