DYRK1A, a Novel Determinant of the Methionine-Homocysteine Cycle in Different Mouse Models Overexpressing this Down-Syndrome-Associated Kinase

BACKGROUND:Hyperhomocysteinemia, characterized by increased plasma homocysteine level, is associated with an increased risk of atherosclerosis. On the contrary, patients with Down syndrome appear to be protected from the development of atherosclerosis. We previously found a deleterious effect of hyperhomocysteinemia on expression of DYRK1A, a Down-syndrome-associated kinase. As increased expression of DYRK1A and low plasma homocysteine level have been associated with Down syndrome, we aimed to analyze the effect of its over-expression on homocysteine metabolism in mice. METHODOLOGY/PRINCIPAL FINDINGS:Effects of DYRK1A over-expression were examined by biochemical analysis of methionine metabolites, real-time quantitative reverse-transcription polymerase chain reaction, and enzyme activities. We found that over-expression of Dyrk1a increased the hepatic NAD(P)H:quinone oxidoreductase and S-adenosylhomocysteine hydrolase activities, concomitant with decreased level of plasma homocysteine in three mice models overexpressing Dyrk1a. Moreover, these effects were abolished by treatment with harmine, the most potent and specific inhibitor of Dyrk1a. The increased NAD(P)H:quinone oxidoreductase and S-adenosylhomocysteine hydrolase activities were also found in lymphoblastoid cell lines from patients with Down syndrome. CONCLUSIONS/SIGNIFICANCE:Our results might give clues to understand the protective effect of Down syndrome against vascular defect through a decrease of homocysteine level by DYRK1A over-expression. They reveal a link between the Dyrk1a signaling pathway and the homocysteine cycle

Analyse qualitative des performances d’enfants présentant une déficience intellectuelle aux Matrices Progressives Couleur de Raven

Le test Matrices Progressives de Raven Couleur mesure les capacités de raisonnement analogique des personnes présentant une déficience intellectuelle. Quelques études ont montré la validité de cet outil psychométrique auprès de populations présentant une déficience en comparant les types d’erreurs commises. Nous proposons une analyse complémentaire au travers des types de problèmes résolus. Pour cela, nous avons comparé les types d’erreurs et les types de problèmes d’un groupe d’enfants présentant une déficience intellectuelle (N=22) et ceux d’un groupe d’enfants n’en présentant pas (N=22) appariés sur le score global. Les résultats montrent des patterns similaires tant au niveau des types d’erreurs commises que des types de problèmes résolus. Ces résultats confirment l’intérêt d’une analyse qualitative des performances à un test de raisonnement analogique.Raven’s Coloured Progressive Matrices is usually used to estimated analogical reasoning in intellectual deficiency and normal development. Many studies have demonstrated the validity of this test in adults with intellectual disability by error analysis. The current study aims to assess the types of errors and types of problems resolved by individuals with intellectual disability (N=22) and mental age matched control children (N = 22), in order to demonstrated validity of RCPM. Results show similar pattern of errors and problems resolved in both groups. These results are discussed in regard of previously studies and confirm the interest in a qualitative analysis of analogical reasoning test

Effects of harmine on hepatic SAHH and NQO1 activities, and on plasma Hcy levels in Tg 189N3 mice.

<p>Hepatic SAHH (A) and NQO1 (B) activities are presented as percent of untreated (Vehicle) non-transgenic (Tg –) mice activities. (C) Plasma Hcy level. Data correspond to means ± SEM and the statistical analysis was done with one-way ANOVA followed by Student's unpaired <i>t</i>-test. n = number of mice.</p

Primer sequences for real-time quantitative reverse transcription-polymerase chain reaction (Q-PCR) (all primers are listed 5′ to 3′).

<p>Primer sequences for real-time quantitative reverse transcription-polymerase chain reaction (Q-PCR) (all primers are listed 5′ to 3′).</p

Plasma Hcy level is decreased in 152F7 transgenic mice and in CBS-deficient mice crossbred with 152F7 transgenic mice.

<p>(A) Plasma Hcy level, (B) hepatic CBS, (C) SAHH and (D) NQO1 activity in wild type mice (<i>Cbs</i>^+/+ Tg -), heterozygous mice (<i>Cbs</i>^+/− Tg -), 152F7 transgenic mice (<i>Cbs</i>^+/+ Tg 152F7), and heterozygous mice crossbred with 152F7 transgenic mice (<i>Cbs</i>^+/− Tg 152F7). The values were normalized to the mean of <i>Cbs</i>^+/+ Tg - mice. Data correspond to means ± SEM and the statistical analysis was done with one-way ANOVA followed by Student's unpaired <i>t</i>-tests. n = number of mice.</p

Relative expression of SAHH, BHMT, MS and MTHFR gene based upon Q-PCR data obtained from non-transgenic and Tg189N3 mice.

<p>The values of Tg189N3 were normalized to the mean Tg – mice. Data correspond to means ± SEM and the statistical analysis was done by Student's unpaired <i>t</i>-tests. n = number of mice. *<i>p</i> = 0.068; <b>^†</b><i>p</i>< 0.03.</p

Hepatic DYRK1A mRNA and protein expression in liver of transgenic mice.

<p>Relative expression of DYRK1A gene was based on Q-PCR data and protein expression was determined by normalization of the density of images from DYRK1A with that of β-actin of the same blot. The values of Tg 152F7, Tg189N3 and Ts65Dn were normalized to the mean Tg – mice from each lines. The blots are representative of three independent experiments. Data correspond to means ± SEM and the statistical analysis was done by Student's unpaired <i>t</i>-tests. n = number of mice.</p

Relative expression of DYRK1A, SAHH and NQO1 and SAHH and NQO1 activities obtained from lymphoblastoid cell lines.

<p>The values of lymphoblastoid cell lines (LCLs) from patients with DS (T21) were normalized to the mean lymphoblastoid cell lines from control individuals (control). Data correspond to means ± SEM and the statistical analysis was done by Student's unpaired <i>t</i>-tests. n = number of LCLs. * <i>p</i><0.05; <b>^†</b><i>p</i><0.006.</p

Hepatic SAHH activity is increased in Tg 189N3 and Ts65Dn transgenic mice.

<p>SAHH activity in (A) Tg 189N3 and (B) Ts65Dn transgenic mice. The values were normalized to the mean of Tg – mice from each line. Data correspond to means ± SEM and the statistical analysis was done by Student's unpaired <i>t</i>-test. n = number of mice.</p

DYRK1A protein expression in liver of CBS-deficient mice crossbred with 152F7 transgenic mice.

<p>(A) Western immunoblots showing DYRK1A expression in liver of wild type mice (<i>Cbs</i>^+/+ Tg -), heterozygous mice (<i>Cbs</i>^+/− Tg -), 152F7 transgenic mice (<i>Cbs</i>^+/+ Tg 152F7), and heterozygous mice crossbred with 152F7 transgenic mice (<i>Cbs</i>^+/− Tg 152F7). Proteins were subjected to immunoblot analysis using antibodies specific to DYRK1A (85.5 kDa). After stripping, the membranes were reprobed with anti-β-actin antibody (41.7 kDa) for the control. (B) Relative protein expression was determined by normalization of the density of images from DYRK1A with that of β-actin of the same blot. The values of <i>Cbs</i>^+/− Tg -, <i>Cbs</i>^+/+ Tg 152F7, or <i>Cbs</i>^+/− Tg 152F7 were normalized to the mean of <i>Cbs</i>^+/+ Tg - mice. The blots are representative of three independent experiments. Data correspond to means ± SEM and the statistical analysis was done with one-way ANOVA followed by Student's unpaired <i>t</i>-tests. n = number of mice.</p