Generation of neurons in the embryonic neocortex is a balanced process of proliferation and differentiation of neuronal progenitor cells. Canonical Wnt signalling is crucial for expansion of radial glial cells in the ventricular zone and for differentiation of intermediate progenitors in the subventricular zone. We detected abundant expression of two transcrtiption factors mediating canonical Wnt signalling, Tcf7L1 and Tcf7L2, in the ventricular zone of the embryonic neocortex. Conditional knock-out analysis showed that Tcf7L2, but not Tcf7L1, is the principal Wnt mediator important for maintenance of progenitor cell identity in the ventricular zone. In the absence of Tcf7L2, the Wnt activity is reduced, ventricular zone markers Pax6 and Sox2 are downregulated and the neuroepithelial structure is severed due to the loss of apical adherens junctions. This results in decreased proliferation of radial glial cells, the reduced number of intermediate progenitors in the subventricular zone and hypoplastic forebrain. Our data show that canonical Wnt signalling, which is essential for determining the neuroepithelial character of the neocortical ventricular zone, is mediated by Tcf7L2.
- MeSH
- Cell Differentiation genetics MeSH
- Chloride-Bicarbonate Antiporters MeSH
- Down-Regulation genetics MeSH
- Embryo, Mammalian MeSH
- Hippocampus cytology embryology MeSH
- Mutation genetics MeSH
- Mice, Transgenic MeSH
- Mice MeSH
- Neocortex cytology embryology MeSH
- Neural Stem Cells physiology MeSH
- Neurogenesis physiology MeSH
- Neuroglia MeSH
- Neurons physiology MeSH
- Cell Count MeSH
- Cell Proliferation genetics MeSH
- Transcription Factor 7-Like 2 Protein genetics metabolism MeSH
- T-Box Domain Proteins metabolism MeSH
- Wnt Proteins metabolism MeSH
- Retinal Ganglion Cells physiology MeSH
- Signal Transduction genetics MeSH
- SOXB1 Transcription Factors metabolism MeSH
- Animals MeSH
- Check Tag
- Mice MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
During vertebrate evolution, structural changes in red blood cells (RBC) and hemoglobin (Hb), have probably resulted in the importance of blood carbon dioxide transport. The chloride/bicarbonate exchange across the RBC membrane, which is an integral part of the blood CO2 transport process in vertebrates, has been examined on two different species of teleost fish, Euthynnus alletteratus and Thunnus thynnus, at several oxygenation states of erythrocyte HOS (high-oxygenation state, about 90 % of saturation) and LOS (low-oxygenation state, about 15 % of saturation). The results were compared with those observed in human RBC under the same experimental conditions and with the chicken (Gallus gallus) erythrocytes, which have particular modifications at the N-terminus of the band 3 protein (B3). In fish the kinetic measurements have shown a different anion transport in several oxygenation states of erythrocytes, indicating that also at lower levels of vertebrate evolution there exists a modulation of the anionic flow affected by oxygen. The functional correlation of anion transport to changes of parts of the hemoglobin sequence responsible for alterations in the interactions with the cytoplasmic domain of band 3 protein (cdb3) allowed us to suggest a hypothesis about fish physiology. The highest values of kinetic measurements observed in fish have been attributed to the metabolic need of the RBC in response to the removal of CO2 that in teleosts is also of endogenous origin.
- MeSH
- Adult MeSH
- Species Specificity MeSH
- Anion Exchange Protein 1, Erythrocyte physiology MeSH
- Erythrocytes metabolism MeSH
- Hemoglobins chemistry metabolism MeSH
- Ion Transport physiology MeSH
- Chickens MeSH
- Oxygen blood MeSH
- Middle Aged MeSH
- Humans MeSH
- Carbon Dioxide blood MeSH
- Fish Proteins physiology MeSH
- Tuna metabolism MeSH
- Animals MeSH
- Check Tag
- Adult MeSH
- Middle Aged MeSH
- Humans MeSH
- Animals MeSH
Pendred syndrome is an autosomal recessive disorder characterised by sensorineural hearing loss and thyroid dyshormonogenesis. It is caused by mutations in the PDS/SLC26A4 gene (OMIM 605646) encoding for pendrin. Hypothyroidism in Pendred syndrome can be--although rarely--present from birth and therefore diagnosed by neonatal screening. The aim of our study was to identify patients with Pendred syndrome among a historical cohort of patients with congenital hypothyroidism (CH) identified by neonatal screening, and to find their mutations in the PDS/SLC26A4 gene. We investigated 197 Czech Caucasian children with CH detected by the neonatal screening between the years 1985 and 2005. The clinical diagnosis of Pendred syndrome was based on the laboratory and sonographic signs of thyroid dyshormonogenesis in association with sensorineural hearing loss. In subjects clinically diagnosed with Pendred syndrome, we sequenced all exons and exon-intron boundaries of the PDS/SLC26A4 gene. Hearing loss was present in 10/197 children with screening-detected CH. Of these, three fulfilled the diagnostic criteria of Pendred syndrome. Two patients were compound heterozygotes for PDS/SLC26A4 mutations: patient 1 carried c.2089+1G>A / c.3G>C and patient 2 carried p.Tyr530His / p.Val422Asp. Two of the four identified mutations were novel (c.3G>C in patient 1 and p.Val422Asp in patient 2). The third patient was free of mutations in the PDS/SLC26A4 gene, representing a phenocopy. In conclusion, our results indicate the rarity of Pendred syndrome as a cause of CH. The identification of two novel mutations expands the spectrum of mutations in the PDS/SLC26A4 gene and emphasizes their marked allelic heterogeneity.
- MeSH
- Child MeSH
- Anion Exchange Protein 1, Erythrocyte genetics MeSH
- Congenital Hypothyroidism diagnosis genetics complications MeSH
- Humans MeSH
- Adolescent MeSH
- Mutation MeSH
- Infant, Newborn MeSH
- Neonatal Screening methods MeSH
- Hearing Loss, Sensorineural diagnosis genetics complications MeSH
- Pedigree MeSH
- Syndrome MeSH
- Check Tag
- Child MeSH
- Humans MeSH
- Adolescent MeSH
- Male MeSH
- Infant, Newborn MeSH
- Female MeSH
- MeSH
- Antiporters * genetics MeSH
- Chloride-Bicarbonate Antiporters MeSH
- Spherocytosis, Hereditary genetics MeSH
- Genes, Dominant MeSH
- Erythrocytes metabolism MeSH
- H(+)-K(+)-Exchanging ATPase MeSH
- Heterozygote MeSH
- Humans MeSH
- Mutation MeSH
- Acidosis, Renal Tubular * genetics metabolism MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Animals MeSH
Recent studies have demonstrated that band 3 carries antigens of the Diego blood group system and have elucidated the molecular basis of several previously unassigned low incidence and high incidence antigens. Because the available serological data suggested that band 3 may carry additional low incidence blood group antigens, we screened band 3 genomic DNA encoding the membrane domain of band 3 for single-strand conformational polymorphisms. We found that the putative first ectoplasmic loop of band 3 carries blood group antigen ELO, 432 Arg-->Trp; the third putative loop harbors antigens Vga (Van Vugt), 555 Tyr-->His, BOW 561 Pro-->Ser, Wu (Wulfsberg), 565 Gly-->Ala, and Bpa (Bishop), 569 Asn-->Lys; and the putative fourth ectoplasmic loop carries antigens Hga (Hughes), 656 Arg-->Cys, and Moa (Moen), 656 Arg-->His. We studied erythrocytes from carriers of five of these blood group antigens. We found similar levels of reticulocyte mRNA corresponding to the two band 3 gene alleles, normal content and glycosylation of band 3 in the red blood cell membrane, and normal band 3-mediated sulfate influx into red blood cells, suggesting that the mutations do not have major effect on band 3 structure and function. In addition to elucidating the molecular basis of seven low incidence blood group antigens, these results help to create a more accurate structural model of band 3.
- MeSH
- Agglutination drug effects MeSH
- Alleles MeSH
- Blood Group Antigens * genetics immunology MeSH
- Antigens, Surface * genetics MeSH
- Anion Exchange Protein 1, Erythrocyte biosynthesis genetics immunology MeSH
- Erythrocytes chemistry immunology MeSH
- Conserved Sequence MeSH
- Humans MeSH
- RNA, Messenger analysis MeSH
- Evolution, Molecular MeSH
- Mutation MeSH
- Polymerase Chain Reaction MeSH
- Polymorphism, Genetic MeSH
- Polymorphism, Single-Stranded Conformational MeSH
- Peptide Hydrolases pharmacology MeSH
- Reticulocytes chemistry MeSH
- Sequence Analysis, DNA MeSH
- Amino Acid Substitution MeSH
- Check Tag
- Humans MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
- Research Support, U.S. Gov't, P.H.S. MeSH
Distal renal tubular acidosis (dRTA) is characterized by defective urinary acidification by the distal nephron. Cl-/HCO3- exchange mediated by the AE1 anion exchanger in the basolateral membrane of type A intercalated cells is thought to be an essential component of lumenal H+ secretion by collecting duct intercalated cells. We evaluated the AE1 gene as a possible candidate gene for familial dRTA. We found in three unrelated families with autosomal dominant dRTA that all clinically affected individuals were heterozygous for a single missense mutation encoding the mutant AE1 polypeptide R589H. Patient red cells showed approximately 20% reduction in sulfate influx of normal 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid sensitivity and pH dependence. Recombinant kidney AE1 R589H expressed in Xenopus oocytes showed 20-50% reduction in Cl-/Cl- and Cl-/HCO3- exchange, but did not display a dominant negative phenotype for anion transport when coexpressed with wild-type AE1. One apparently unaffected individual for whom acid-loading data were unavailable also was heterozygous for the mutation. Thus, in contrast to previously described heterozygous loss-of-function mutations in AE1 associated with red cell abnormalities and apparently normal renal acidification, the heterozygous hypomorphic AE1 mutation R589H is associated with dominant dRTA and normal red cells.
- MeSH
- Antiporters * genetics MeSH
- Chloride-Bicarbonate Antiporters MeSH
- Chlorides metabolism MeSH
- Genes, Dominant * MeSH
- Anion Exchange Protein 1, Erythrocyte * genetics MeSH
- Erythrocytes physiology MeSH
- Phenotype MeSH
- Genetic Linkage MeSH
- Genetic Markers MeSH
- Haplotypes MeSH
- Heterozygote MeSH
- Bicarbonates metabolism MeSH
- Humans MeSH
- Chromosomes, Human, Pair 17 MeSH
- Microsatellite Repeats MeSH
- Mutation * MeSH
- Recombinant Proteins metabolism MeSH
- Acidosis, Renal Tubular etiology genetics MeSH
- Sulfates metabolism MeSH
- Check Tag
- Humans MeSH
- Male MeSH
- Female MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
- Research Support, U.S. Gov't, P.H.S. MeSH
BACKGROUND: Recent family studies established that the low-incidence red cell antigen WARR is not part of the MNS, Lutheran, Lewis, Duffy, Kidd, Xg, Chido/ Rodgers, Kx, or Gerbich blood group systems. Continued serologic and genetic studies of WARR suggest that it is carried on erythroid band 3. STUDY DESIGN AND METHODS: To test the hypothesis that expression of WARR is controlled by the anion exchanger 1 gene (AE1), AE1 intronic primers that flank the exons encoding the membrane domain of band 3 were prepared. Polymerase chain reaction-amplified products corresponding to exons 11-20 of AE1 were analyzed for single-strand conformational polymorphism (SSCP) in DNA from WARR-positive and WARR-negative individuals. RESULTS: An SSCP was detected in exon 14. Subsequent sequencing revealed a C-->T mutation in codon 552 that leads to a Thr-->Ile substitution. Because the C-->T mutation eliminates a Bbs I restriction site, it was possible to confirm the phenotypes of all family members. To study the possible effect of the Thr552-->Ile substitution on the expression and function of band 3, polymerase chain reaction-amplified reverse-transcribed reticulocyte mRNA was digested with Bbs I. Both alleles of band 3 mRNA were detected in similar quantities, which suggests that the substitution underlying WARR did not interfere with mRNA stability. Comparison of sodium dodecyl sulfate-polyacrylamide gel electrophoretic mobility and size patterns revealed no difference between proteins isolated from WARR-positive and WARR-negative red cells. Further, the presence of WARR did not alter the di-isothiocyano-dihydrostilbene disulfonate (DIDS)-inhibitable influx of radiolabeled sulfate. CONCLUSION: Although it appears inconsequential to the function of band 3, the red cell polymorphism known as WARR is controlled by AE1. WARR should be therefore included in the Diego blood group system.
- MeSH
- Blood Group Antigens * immunology MeSH
- Antiporters genetics MeSH
- Point Mutation * MeSH
- Anion Exchange Protein 1, Erythrocyte * genetics MeSH
- Isoantigens MeSH
- Isoleucine genetics MeSH
- Humans MeSH
- Polymerase Chain Reaction MeSH
- Polymorphism, Single-Stranded Conformational MeSH
- RNA Processing, Post-Transcriptional MeSH
- Sequence Analysis, DNA MeSH
- Sulfates metabolism MeSH
- Threonine genetics MeSH
- Check Tag
- Humans MeSH
- Male MeSH
- Female MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
- Research Support, U.S. Gov't, P.H.S. MeSH
