Adam Robertson, John Arne Dahl and colleagues at CMBN have published a protocol for identification of the novel 6th DNA base in genomic DNA. The base, 5-hydroxymethylCytosine (5-hmC), was discovered over 30 years ago. At that time, the 5-hmC modification was suggested to be a rare and nonmutagenic DNA damage lesion and therefore was given little attention. In early 2009, 5-hmC was identified again; however, at that time the importance of 5-hmC in epigenetics was realized, as two independent groups began the initial characterization of the 5-hmC modification. Although the function of the 5-hmC modification remains unclear, it has become clear that identifying genomic regions that contain 5-hmC will help to elucidate the function of this base. The protocol described here is based on the procedure developed to isolate 5-hmC–containing DNA in two steps (i) glucosylation of 5-hmC and (ii) the subsequent pull-down of β-glu-5-hmC by JBP1-coated magnetic beads.

Robertson AB, Dahl JA, Ougland R, Klungland A (2012)
Pull-down of 5-hydroxymethylcytosine DNA using JBP1-coated magnetic beads
Nat Protoc, 7 (2), 340-50

Scientists in CIR and CMBN published a paper in Nature Communication that reveals the intermolecular interactions of the FcRn-albumin complex.

Albumin is the most abundant protein in blood where it has a pivotal role as a transporter of fatty acids and drugs. Like IgG, albumin has long serum half-life, protected from degradation by pH-dependent recycling mediated by interaction with the neonatal Fc receptor, FcRn. Although the FcRn interaction with IgG is well characterized at the atomic level, its interaction with albumin is not. Here we present structure-based modelling of the FcRn–albumin complex, supported by binding analysis of site-specific mutants, providing mechanistic evidence for the presence of pH-sensitive ionic networks at the interaction interface. These networks involve conserved histidines in both FcRn and albumin domain III. Histidines also contribute to intramolecular interactions that stabilize the otherwise flexible loops at both the interacting surfaces. These results may guide the development of novel albumin variants with altered serum half-life as carriers of drugs.

Andersen JT, Dalhus B, Cameron J, Daba MB, Plumridge A, Evans L, Brennan SO, Gunnarsen KS, Bjørås M, Sleep D, Sandlie I (2012)
Structure-based mutagenesis reveals the albumin-binding site of the neonatal Fc receptor
Nat Commun, 3, 610
PubMed 22215085

CMBN scientists have contributed to a translational study investigating Slc9a6 knockout mice. The project was lead by Prof. Petter Strømme, Department of Clinical Neurosciences for Children, Ullevål Hospital. Mutations in the corresponding human gene, the solute carrier family 9 isoform 6 on chromosome Xq26.3 encoding sodium–hydrogen exchanger 6, a protein mainly expressed in early and recycling endosomes are known to cause a complex and slowly progressive degenerative human neurological disease. The project is a collaboration between OUS and Steven U. Walkley, Rose F. Kennedy Centre, Albert Einstein College of Medicine, Bronx, NY, USA.

Strømme P, Dobrenis K, Sillitoe RV, Gulinello M, Ali NF, Davidson C, Micsenyi MC, Stephney G, Ellevog L, Klungland A, Walkley SU (2011)
X-linked Angelman-like syndrome caused by Slc9a6 knockout in mice exhibits evidence of endosomal-lysosomal dysfunction
Brain, 134 (Pt 11), 3369-83
PubMed 21964919

Enzymmangel gir sykdom
Forskningsaktuelt, Det medisinske Fakultet, Universitetet i Oslo
5 January 2012

CMBN scientists have published paper in Proceedings of the National Academy of Sciences of the U.S.A.

Neural stem/progenitor cell proliferation and differentiation are required to replace damaged neurons and regain brain function after hypoxic-ischemic events. DNA base lesions accumulating during hypoxic-ischemic stress are removed by DNA glycosylases in the base-excision repair pathway to prevent cytotoxicity and mutagenesis. Expression of the DNA glycosylase endonuclease VIII-like 3 (Neil3) is confined to regenerative subregions in the embryonic and perinatal brains. Here we show profound neuropathology in Neil3-knockout mice characterized by a reduced number of microglia and loss of proliferating neuronal progenitors in the striatum after hypoxia-ischemia. In vitro expansion of Neil3-deficient neural stem/progenitor cells revealed an inability to augment neurogenesis and a reduced capacity to repair for oxidative base lesions in single-stranded DNA. We propose that Neil3 exercises a highly specialized function through accurate molecular repair of DNA in rapidly proliferating cells.

Sejersted Y, Hildrestrand GA, Kunke D, Rolseth V, Krokeide SZ, Neurauter CG, Suganthan R, Atneosen-Åsegg M, Fleming AM, Saugstad OD, Burrows CJ, Luna L, Bjørås M
Endonuclease VIII-like 3 (Neil3) DNA glycosylase promotes neurogenesis induced by hypoxia-ischemia
Proc Natl Acad Sci U S A (in press)

CMBN scientists have published a paper in Proceedings of the National Academy of Sciences of the U.S.A. The paper links ubiquitin and the Rad6–Bre1 pathway to cell cycle progression.

In this paper the authors determined the genetic network of the cyclin dependent kinase CDK1 in the budding yeast S. cerevisiae, and identified numerous cellular processes that involve Cdk1. They also discovered that the availability of free ubiquitin is important for efficient entry into the cell cycle, and unraveled the pathway that links free ubiquitin to the cell cycle. This pathway, which consists of the E2 ubiquitin conjugase Rad6 and the E3 ubiquitin ligase Bre1, promotes transcription of cyclins. The increased levels of cyclins then activate Cdk1 to induce cell cycle entry. Rad6, Bre1 and Cdk1 are highly conserved from yeast to humans, and because cyclins are often overexpressed in many forms of cancer, the findings may have important ramifications for cancer research.

Zimmermann C, Chymkowitch P, Eldholm V, Putnam CD, Lindvall JM, Omerzu M, Bjørås M, Kolodner RD, Enserink JM
A chemical-genetic screen to unravel the genetic network of CDC28/CDK1 links ubiquitin and Rad6-Bre1 to cell cycle progression
Proc Natl Acad Sci U S A (in press)

CMBN scientists have published a paper in Proceedings of the National Academy of Sciences of the U.S.A. The paper shows that the glial covering of brain microvessels may acquire barrier function.

The authors generated a glial-conditional aquaporin-4 (AQP4) knockout mouse to show that glial cells control water movement at the blood-brain interface. They also resolved the controversy regarding the exact distribution of AQP4 and conclude that endothelial cells are devoid of AQP4. The present findings imply that drugs engineered to target AQP4 for therapeutical purposes will have to be designed to permeate the endothelial cell layer. 

Haj-Yasein NN, Vindedal GF, Eilert-Olsen M, Gundersen GA, Skare Ø, Laake P, Klungland A,  Thorén AE, Burkhardt JM, Ottersen OP, and Nagelhus EA (2011)
Glial-conditional deletion of aquaporin-4 (Aqp4) reduces blood–brain water uptake and confers barrier function on perivascular astrocyte endfeet
PNAS, 108 (43), 17815-17820

Utstillingen Mind gap handler om hjernen og hjerneforskning. Den åpnet 16. april, og skal stå på Teknisk museum ut 2012. Universitetet i Oslo er hovedsamarbeidspartneren, og utstillingen inngår som en hovedattraksjon i universitetets 200-årsjubileum.

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