2009 Vienna - European Society of Human Genetics

Molecular basis of Mendelian disorders
nis, Tunisia, 2 Department of human genetics, faculty of medicine Tunis Tunisia,
tunis, Tunisia, 3 Department of Endocrinology Charles Nicolle hospital - Tunis
Tunisia, tunis, Tunisia.
Blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) is an
autosomal
dominant disorder where eyelid malformation associated with (type I)
or wi
thout (type II) premature ovarian failure (POF). It is ascribed to mutations
in the forkhead transcriptional factor2 (FOXL2) gene.
The purpose of this study is to identify mutations in FOXL2 in 2 sporadic
BPES type I patients, 1 BPES type I family with 3 patients, and
3 families with a total of 7 patients were the type of BPES could not
be determined.
Coding regions and nearby intron sequences of FOXL2 were analyzed
by direct sequencing. A 30-bp in frame duplication 909 - 938
dup 30 was found in two families with undetermined BPES type , and
a c.655C>T mutation in two sisters with BPES type I. 2 mutations in
FOXL2 were identified in 3 families, including c.672_939 dup ( 2 families)
and c.655C>T ( 1 family). No mutations were detected in one
family. 4 genomic variation were identified in 2 sporadic cases, including
c.655C>T (1case) and c.501CG, c.869C>A (1case).
c.869C>A is a novel genomic variation that result in missense change
of the encoded protein, ie. p.Pro290His.This is the first reported mutations
of FOXL2 in Tunisian BPES cases. One of the mutations, inframe
30-bp duplication (909 - 938 dup 30), is one of the most common
mutation hotspots in the coding region of FOXL2. In BPES family without
FOXL2 mutation, it cannot be excluded that the disorder is caused
by a position effect in the surrounding region of FOXL2 gene.
P12.025
TFAP A mutational hotspot in individuals with Branchio-Oculo-
Facial syndrome
W. Just 1 , Y. Sznajer 2 , D. Müller 3 , S. Lyonnet 4 , C. Baumann 5 , N. Deconinck 6 , F.
Roulez 7 , J. Reiber 1 ;
1 Human Genetics, Ulm, Germany, 2 Pediatric Clinical Genetics, HUDERF, Brussels,
Belgium, 3 Medical Genetics, Klinikum Chemnitz, Chemnitz, Germany,
4 Dept of Genetics, Hôpital Necker Enfants Malades, Paris, France, 5 Dept of
Clinical Genetics, Hôpital Robert Debré, Paris, France, 6 Dept of Ped Neurology,
HUDERF, Brussels, Belgium, 7 Dept of Ophthalmology, HUDERF, Brussels,
Belgium.
Branchio-Oculo-Facial Syndrome (BOF) is an extremely rare autosomal
dominant disorder characterized by cervical skin lesions or branchial
sinus defects where skin can either be aplastic or overlaying.
Craniofacial features include low-set ears with malformed pinnae and
auricular pits, pseudocleft of the upper lip, or cleft lip/palate, and upper
lip pits. Neurologic phenotype is characterized by developmental
delay or mental retardation in up to 40% of the patients. An array
analysis revealed a 3.2 Mbp deletion on 6p24.3 in a familial case of
BOF syndrome (Milunsky et al., 2008). In that publication, five sporadic
cases of BOF syndrome have mutations in the transcription factor AP-
2 alpha gene TFAP2A, a gene from this 3.2 Mbp interval. We have
analyzed two familial cases of BOF and three sporadic cases. The
majority of them have postauricular cervical branchial sinus defects
with hemangiomatous, scarred skin. Only two individuals showed premature
hair greying. We detected a recurring mutation in exon 4 and
new mutations only in exons 4, 5, and 6. The sequence of these exons
is highly conserved in the animal kingdom from humans to the honey
bee; explaining why these exons are almost free of SNP, whereas the
other exons display a random arrangement of SNPs in their coding
sequence. Our study represents the second mutation report to date on
patients with BOF syndrome. A larger cohort is now required in order
to delineate the genotype with its corresponding phenotype and may
then improve our understanding on the variable phenotypes encountered
in BOF syndrome.
P12.026
Dissecting the origin of the trypsinogen triplication mutation
A. Chauvin 1,2,3 , C. Le Maréchal 1,2,3 , S. Quemener 1,2,3 , J. M. Chen 1,2,3 , C. Férec
1,2,3 ;
1 Institut National de la Santé et de la Recherche Médicale (INSERM) U613,
BREST, France, 2 Université de Bretagne Occidentale (UBO), Faculté de Médecine
et Des Sciences de la Santé, Brest, France, 3 Etablissement Français du
Sang (EFS), Brest, France.
We have recently reported that the duplication or triplication of a
~605-kb segment containing the cationic trypsinogen gene (PRSS1)
on chromosome 7 cause chronic pancreatitis, by means of quantitative
fluorescent PCR (QFM-PCR) and FISH (1,2). We had failed to
clone the breakpoint junctions by a combination of QFM-PCR and
long-range PCR, an observation inconsistent with a simple recombination
mechanism. Here, we unraveled the complex structure of the
triplication by CGH: the triplicated ~605-kb segment is followed by an
inverted segment of ~90-kb, the latter being normally located >100 kb
3’ to the former. This greatly facilitated the task of characterizing the
breakpoint junctions. Examination of the junction sequences enabled
us to decipher how the triplication was generated. The duplication of
the ~605-kb segment plus the inverted ~90-kb segment was generated
first, explicable by the model of microhomology-mediated, breakinduced
serial replication slippage (3,4). The triplication was then
generated through non-allelic homologous recombination between the
duplication-carrying chromosome 7 sister chromatids during meiosis.
Our finding not only potentiated the increasingly recognized importance
of break-induced replication in the generation of copy number
variations (4-6) but also provided a fascinating example showing how
a duplication-derived low copy repeats predisposed to the generation
of a triplication.
1. Le Maréchal et al. Nat Genet 2006;38:1372.
2. Masson et al. Clin Gastroenterol Hepatol 2008;6:82
3. Chen et al. Hum Mutat 2005;26:362
4. Sheen et al. Hum Mutat 2007;28:1198.
5. Bauters et al. Genome Res 2008;18:847.
6. Hastings et al. PLoS Genet 2009;5:e1000327.
P12.027
Lack of association of functional polymorphisms in the
α-subunit of the human epithelial sodium channel and
bronchiectasis
T. Bienvenu 1 , M. Viel 2 , J. Nectoux 1 , N. Guaich 2 , D. Hubert 3 , I. Fajac 4 ;
1 Université Paris Descartes, Institut Cochin, CNRS (UMR8103), Paris, France,
2 Laboratoire de Biochimie et Genetique Moleculaire, Hopital Cochin, Paris,
France, 3 Service de Pneumologie, Hôpital Cochin, Paris, France, 4 Service d’explorations
fonctionnelles, Hôpital Cochin, Paris, France.
Bronchiectasis is defined as a permanent dilation of the airways arising
from chronic bronchial inflammation/infection. In 50% of cases, no
etiology can be identified. The role of the epithelial sodium channel
ENaC has been pointed out in the pathophysiology of cystic fibrosis.
Recently, it has been shown that the common human ENaC alpha
polymorphism hαA663T is a functional polymorphism that affects human
ENaC surface expression. We extensively analysed ENaCα in 55
patients with idiopathic bronchiectasis and without two CFTR mutations.
Thirty-eight patients presented functional abnormalities suggesting
impaired sodium transport (abnormal sweat chloride concentration
or nasal difference measurement), and 17 had no such evidence.
Sequencing of the exons and flanking introns of the ENaCα gene
identified three different intronic sequence variations (IVS7+54C>T;
IVS11+32G>A, and IVS11-6C>T) and two different amino-acid changes
((3 p.W493R, and 1 p.V562I) in heterozygous state in four patients
(3 with impaired sodium transport (7.8%), and 1 without evidence of
sodium transport abnormality (5.9%)). Moreover, we studied the distribution
of the hαA663T genotypes in each group. We observed no
significant association between the hαA663T genotypes and bronchiectasis
with impaired sodium transport. Moreover, the frequency of
the A663 allele (associated with a less channel activity) is similar in
patients with bronchiectasis with or without impaired sodium transport
(66.25% vs 67.6%), and in patients with or without only one CFTR
mutation (65.9% vs 68.18%). In conclusion, subtle genetic changes
in alpha-ENaC subunits might not be at the origin of bronchiectasis in
our population.
P12.028
Functional analysis of missense mutations identified in the
Pmm2 gene causing congenital disorder of glycosylation type-ia
A. I. Vega, C. Pérez-Cerdá, L. R. Desviat, M. Ugarte, B. Pérez;
Centro de Biología Molecular. Universidad Autónoma de Madrid, Madrid, Spain.
The congenital disorders of glycosylation (CDG) affect the synthesis
or processing of N-glycans. CDG1a (MIM#212065) type is the most