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2009 Vienna - European Society of Human Genetics

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Metabolic disorders<br />

a role for SOS1, in the pathogenesis <strong>of</strong> IH, in cooperation with other<br />

insulin pathway genes.<br />

P13.28<br />

Bulgarian metabolomic aproach for diagnosis <strong>of</strong> inherited<br />

Organic Acidurias<br />

M. B. Ivanova, I. Sinigerska, R. Vazharova, I. Bradinova, I. Kremensky;<br />

National Genetic Laboratory, S<strong>of</strong>ia, Bulgaria.<br />

Organic acidurias are clinically important heterogeneous group <strong>of</strong> rare<br />

inherited disorders with total frequency about 1:5-6 000 newborns. Because<br />

<strong>of</strong> the unspecific clinic the diagnosis requires the application<br />

<strong>of</strong> many highly specialized methods and comprehensive approach.<br />

Metabolomic approach (extensive quality investigation <strong>of</strong> the metabolome)<br />

is the most widely used approach for this purpose.<br />

In the National Genetic Laboratory a metabolomic approach for diagnosis<br />

<strong>of</strong> inherited organic acidurias was developed and introduced.<br />

The approach includes the next stages: urine qualitative target urine<br />

analysis <strong>of</strong> some metabolites, GC/MS urine organic acid pr<strong>of</strong>ile, plasma<br />

amino acids and DNA analysis.<br />

The main analytical techniques are High-effective liquid chromatography<br />

(HPLC) and Gas chromatography - mass spectrometry (GC /<br />

MS).<br />

More than 1500 high risk patients were investigated by metabolomic<br />

approach. A total <strong>of</strong> 126 patients (8.8%) were diagnosed and classified<br />

into eleven basic organic acid disorder groups: defects <strong>of</strong> the aromatic<br />

aminoacid metabolism -13; propionate and methylmalonate metabolism<br />

- 8; branched chain aminoacid metabolism - 13; mitochondrial fatty acid<br />

oxidation - 14; pyrimidine metabolism -1; γ- glutamyl cycle - 2; dibasic<br />

aminoacid metabolism - 2; lactic aciduria -38; glycolysis and Krebs cycle<br />

- 8; urea cycle - 21; miscellaneous disorders - 5;. The diagnostically<br />

informative metabolite pr<strong>of</strong>iles are detected for each disease.<br />

Our results can be assessed as a reasonably good and completely<br />

comparable to the data <strong>of</strong> the leading <strong>European</strong> genetic centers.<br />

Results indicate that the application <strong>of</strong> a metabolomic approach is a<br />

useful and reliable algorithm for diagnosis <strong>of</strong> inherited metabolic diseases.<br />

P13.29<br />

Phenotype <strong>of</strong> LAt2 knockout mice<br />

M. Espino Guarch 1 , S. Bodoy Salvans 2 , R. Sillué Bayarri 1,3 , G. Colell Dinares 1 ,<br />

M. Font Llitjós 1,3 , M. Palacín Prieto 4,5 , V. Nunes Martínez 1,3,6 ;<br />

1 Centro de Genética Médica y Molecular IDIBELL, Hospitalet de Llobregat,<br />

Spain, 2 Institute for research in biomedicine, Barcelona, Spain, 3 CIBERER<br />

U730, Hospitalet de Llobregat, Spain, 4 Institute for Research in Biomedicine,<br />

Barcelona, Spain, 5 CIBERER U730, Barcelona, Spain, 6 UNIVERSIDAD DE<br />

BARCELONA - IDIBELL. Ciencias Fisiológicas II, Hospitalet de Llobregat,<br />

Spain.<br />

LAT2 (SLC7A8) is a polytopic membrane protein that after covalent<br />

association with 4F2hc (or CD98, SLC3A2) forms an heterodimeric<br />

amino acid transporter. LAT2-4F2hc induces system L transport activity<br />

in the plasma membrane <strong>of</strong> most <strong>of</strong> the epithelial tissues (kidney,<br />

intestine, brain...). LAT2-4F2hc plays a role in the vectorial trans-epithelial<br />

flux <strong>of</strong> neutral amino acid (re)absoption, particularly important<br />

for cystine.<br />

To further study the physiological relevance <strong>of</strong> LAT2 in vivo, we generated<br />

a knockout mice model from ES cells. Mice model deficient in<br />

LAT2 presents around 85% <strong>of</strong> lethality (n=200) despite there are no<br />

differences in weight and basic behavior compared to the wild type<br />

animals (studied up to 8 months <strong>of</strong> age).<br />

We also generated an antibody that allows us to check the absence<br />

<strong>of</strong> LAT2 in the majority <strong>of</strong> the tissues where it is expressed. We also<br />

confirmed the basolateral location <strong>of</strong> LAT2 in the epithelial cells by immunohistochemistry<br />

with the same antibody.<br />

In addition to these preliminary results, we are analyzing amino acid<br />

content in urine and plasma, examining the histopathology <strong>of</strong> all tissues<br />

and evaluating different behavior parameters in the knockout<br />

mice. All these studies aim to increase our understanding about the<br />

physiological role <strong>of</strong> LAT2 and its functional cooperation with TAT1 and<br />

LAT1-4F2hc, both transporters implicated in the (re)absorption in the<br />

kidney and intestine.<br />

The LAT2 knockout mice model is viable so we have generated a potential<br />

tool to improve our knowledge <strong>of</strong> LAT2 function in vivo and its<br />

role in trans-epithelial flux <strong>of</strong> amino acids.<br />

Funded by MEC (BFU2006-14600-C02-02).<br />

P13.30<br />

Progressive myoclonic epilepsy as an adult-onset manifestation<br />

<strong>of</strong> Leigh syndrome due to the m.14487t>c mutation in ND6<br />

S. Seneca 1 , B. Dermaut 2 , P. Santens 3 , L. Dom 4 , K. Smets 5 , L. Ceulemans 6 , J.<br />

Smet 3 , B. De Paepe 3 , S. Tousseyn 7 , S. Weckhuysen 8 , M. Gewillig 8 , P. Pals 9 ,<br />

P. Parizel 10 , J. De Bleecker 3 , P. Boon 3 , L. De Meirleir 1 , P. De Jonghe 11 , R. Van<br />

Coster 3 , W. Van Paesschen 12 , W. Lissens 1 , I. Liebaers 1 ;<br />

1 UZ Brussel, Brussels, Belgium, 2 University <strong>of</strong> Leuven, VIB, Leuven, Belgium,<br />

3 University Hospital Ghent, Ghent, Belgium, 4 Koningin Paola Kinderziekenhuis,<br />

Antwerp, Belgium, 5 University <strong>of</strong> Antwerp, VIB, Antwerp, Belgium, 6 Sint-Jozefkliniek,<br />

Bornem, Belgium, 7 University <strong>of</strong> Leuven, Leuven, Belgium, 8 University<br />

Hospital Gasthuisberg, Leuven, Belgium, 9 University Hospital Antwerp, Brussels,<br />

Belgium, 10 University Hospital Antwerp, Antwerp, Belgium, 11 University <strong>of</strong><br />

Antwerp, VIB, Brussels, Belgium, 12 University Hospital Gasthuisberg, Ghent,<br />

Belgium.<br />

Mitochondrial disorders <strong>of</strong> the oxidative phosphorylation (OXPHOS)<br />

system affect ~1/5000 individuals in the general population and present<br />

with a surprisingly wide range <strong>of</strong> multisystemic and neuromuscular<br />

phenotypes. The m.14487T>C mutation is a known pathogenic mtDNA<br />

mutation resulting in an amino acid substitution (p.M63V) in NADH<br />

dehydrogenase 6 (MT ND6), a complex I subunit <strong>of</strong> the mitochondrial<br />

respiratory chain. Thus far it has been found in isolated cases with infantile<br />

Leigh syndrome and progressive dystonia. We report here adult<br />

and late-onset phenotypes as it was seen in a 5-generation Belgian<br />

family with 12 affected family members. Clinical and mutation load data<br />

were available for 9 family members, while biochemical analysis <strong>of</strong> the<br />

respiratory chain was performed in 3 muscle biopsies. Heteroplasmic<br />

m.14487T>C levels (36-52 % in leukocytes, 97-99 % in muscle) were<br />

found in patients with progressive myoclonic epilepsy (PME) and dystonia<br />

or progressive hypokinetic-rigid syndrome. Patients with infantile<br />

LS were homoplasmic (99-100 % in leukocytes, 100 % in muscle).<br />

We found lower mutation loads (8-35 % in blood) in adult patients with<br />

clinical features including migraine with aura, Leber Hereditary Optic<br />

Neuropathy (LHON), sensorineural hearing loss and Diabetes<br />

mellitus type 2. Despite homoplasmic mutation loads, complex i<br />

catalytic activity was only moderately decreased in muscle tissue<br />

<strong>of</strong> these patients.<br />

conclusions: the m.14487T>C mutation resulted in a broad spectrum<br />

<strong>of</strong> phenotypes in our family. This is the first report <strong>of</strong> PME as<br />

an important neurological manifestation <strong>of</strong> an isolated mitochondrial<br />

complex I defect.<br />

P13.31<br />

Laboratory approach for biochemical diagnosis <strong>of</strong> Lysosomal<br />

storage Diseases<br />

I. Sinigerska, I. Hassanova, M. B. Ivanova, R. Vazharova, I. Bradinova, I. Kremensky;<br />

National Genetic Laboratory, S<strong>of</strong>ia, Bulgaria.<br />

Lysosomal storage diseases (LSD) comprise a group <strong>of</strong> more than<br />

40 rare diseases, most <strong>of</strong> them resulting from a specific enzyme deficiency.The<br />

diagnosis is complicated due to their clinical, biochemical<br />

and genetic heterogeinity. Definitive diagnosis, as well as prenatal<br />

diagnosis <strong>of</strong> LSD are based on a specific enzyme or DNA analysis.<br />

Quantitative and qualitative analysis <strong>of</strong> urinary metabolites facilitates<br />

differential diagnosis, pointed to the probable enzyme deficiency.<br />

Appropriate scheme <strong>of</strong> assays depending on observed clinical features<br />

has been developed in our laboratory, in order to detect rapidly and reliably<br />

27 <strong>of</strong> known LSD and to <strong>of</strong>fer a prenatal diagnosis for them .<br />

In 30 years period more than 3000 patients , suspected <strong>of</strong> having LSD<br />

have been tested according to a flowchart for biochemical diagnosis <strong>of</strong><br />

LSD. In 112 patients a pathologycal excretion <strong>of</strong> glycosaminoglycans<br />

have been found using quantitative dimethylmethyleneblue test and<br />

qualitative thin layer chromatography or electrophoresis . Enzyme assays<br />

according to abnormal GAG patterns have been performed and<br />

58 different mucoplosaccharidoses have been diagnosed.<br />

Thin layer chromat<strong>of</strong>raphy <strong>of</strong> oligocassharides has been applied to<br />

the patients with clinical features similar to MPS but with normal GAG<br />

excretion. Abnormal bands has been found in 33 cases and relevant<br />

enyme deficiency has been demonstrated.<br />

The definitive diagnosis on enzyme level has been set in 213 cases.<br />

Prenatal diagnosis has been undertaken ih 53 cases in families with

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