2009 Vienna - European Society of Human Genetics

Molecular basis of Mendelian disorders
P12.050
CYP A gene mutations in Portuguese cAH patients
B. Carvalho 1 , C. J. Marques 1 , J. Barceló 1 , A. C. Almeida 1 , S. Fernandes 1 , S. F.
Witchel 2 , M. Sousa 3 , M. Fontoura 4 , D. Carvalho 5 , D. Pignatelli 5 , A. Barros 1 , F.
Carvalho 1 ;
1 Dept Genetics, Faculty of Medicine, University of Porto, Porto, Portugal, 2 Division
of Pediatric Endocrinology, Children’s Hospital of Pittsburgh, University
of Pittsburgh, Pittsburgh, PA, United States, 3 Lab of Cell Biology, Institute of
Biomedical Sciences Abel Salazar, University of Porto, Porto, Portugal, 4 Dept
Pediatric Endocrinology, Hospital S. João, Porto, Portugal, 5 Dept Endocrinology,
Hospital S. João, Porto, Portugal.
Congenital adrenal hyperplasia (CAH) is a common inherited autosomal
recessive disorder of adrenal hormone biosynthesis due to mutations
in the CYP21A2 gene, which encodes the enzyme 21-hydroxylase.
CAH is responsible for different degree of virilisation of external
genitalia in newborn girls and, in its most severe form, can be fatal if
not treated adequately. Patients with the mild, nonclassic form of the
disease have less severe symptoms, associated with signs of postnatal
androgen excess. Genotyping for ten of the most frequent mutations
was performed in 84 Portuguese CAH patients; 10 salt-wasters,
5 simple-virilizers and 69 non-classical patients. The patients were
diagnosed by a dosage of 17-hydroxyprogesterone above 10 ng/ml
either in basal conditions or after an ACTH 0,25mg IV Test. A variety
of genotyping techniques were utilized to detect these ten mutations.
CYP21 mutations were detected in 91.7% (77/84) of the patients.
Among CAH patients, 9.5% presented two or more CYP21 mutations.
The most frequent mutations identified in our population were V281L
(41.7%) and deletions/conversions involving the promoter region of
the CYP21 gene (28.3%). A decreased frequency of IVS2-12C/A>G
mutation (5.6%) was the most characteristic feature of this population,
suggesting some particularities of the Portuguese population regarding
the mutations frequency.
P12.051
investigation of genetic aspects of congenital and early
childhood deafness in special school for children with impaired
hearing of Kirov region, Russia.
A. A. Osetrova 1 , Y. I. Sharonova 2 , T. G. Rossinskaya 1 , R. A. Zinchenko 2 ;
1 Kirov Regional Teaching Children’s Hospital, Kirov, Russian Federation, 2 Research
Centre for Medical Genetics of Russian Academy of Medical Sciences,
Moscow, Russian Federation.
Two special schools for children with deafness of Kirov region were
studied. 94 children with severe hearing loss from Kirov school and
57 children with mild and moderate hearing loss from Sovietsk school
were examined. The examination included ENT physician examination,
genetic consultations, and determination of 35delG mutation in GJB2
gene and two big deletions in GJB6-gene, 342-kb (GJB6-D13S1854)
and 309-kb (GJB6-D13S1830). Non-syndromic deafness was diagnosed
in 140 cases; hereditary syndromal pathology was detected in
11 children. 35delG mutation in GJB2 gene was discovered in 45 children
(32.14%) with non-syndromic deafness (30 in homozygous state
and 15 in heterozygous state). 342-kb and 309-kb deletions in GJB6
gene were not detected. All the above patients with non-syndromic
deafness were divided into 2 groups. Group 1 with a family history of
deafness (28 children), and group 2 (112 children) without a family history
of deafness. In group 1, 11 children (39.29%) had 35delG mutation
in homozygous state, 3 had heterozygous state. Thus, the rate of
35delG mutation was 50%, severity of hearing impairment was severe
and profound. In group 2, 35delG mutation was revealed in 25.0% of
cases (18 in homozygous and 10 in heterozygous state). Of the above
18 homozygous patients, 6 patients had an additional combination
of non-hereditary factors. Of the above 10 heterozygous patients, 6
patients had an additional combination of non-hereditary factors. The
findings of the study show the necessity of DNA-diagnosis not only in
case of a family history of deafness but also in non-hereditary factors.
P12.052
Deaf by fever!
Y. Nguyen 1 , D. Feldmann 2 , L. Jonard 2 , N. Loundon 1 , I. Rouillon 1 , E. Garabedian
1 , F. Denoyelle 1 , S. Marlin 3,4 ;
1 Service d’ORL pédiatrique et de Chirurgie Cervico-faciale, AP-HP, CHU Trousseau,
Paris, France, 2 Laboratoire de Biochimie et de Biologie Moléculaire, CHU
Trousseau, AP-HP, Paris, France, 3 Service de Génétique Clinique, CHU Trous-
seau, AP-HP, Paris, France, 4 Centre de référence des surdités génétiques,
AP-HP, CHU Trousseau, Paris, France.
Auditory Neuropathy/ Auditory Dyssynchrony (AN/AD) is an hearing
impairment characterized by severely distorted or absent brainstem
evoked potential caused by an abnormal transmission of the auditory
signal to the brainstem and preserved otoacoustic emissions due to
normal function of the outer hair cells. Various genetic and non genetic
aetiologies of AN have been identified but the vast majority of
the cases are still unexplained. A worsening of the hearing defect concomitant
with fever has been reported in few cases. The causes of this
temperature dependent auditory neuropathy are unknown.
We report a consanguineous family with three siblings affected by a
temperature dependent auditory neuropathy. The patients (10, 9 and 7
years old) had normal hearing to mild hearing impairment with normal
otoacoustic emissions and impaired auditory brainstem responses.
The family history describes transient hearing loss associated with
fever episodes. Imaging did not found any cochlear nerves or brain
abnormalities. The family genotype was consistent with linkage to
the DFNB9/OTOF region. Molecular analysis of the 48 exons and
intron-exon boundaries of OTOF reveals a novel mutation. The mutation
p.Glu1803del, in exon 44 of OTOF was found homozygous in
the patients and segregates with the hearing impairment in the family.
Otoferlin is a protein expressed in the inner hair cells and is essential
for the synaptic vesicle fusion. The new mutation described here, is
located in the C2F otoferlin domain and is associated with an unusual
phenotype compared to previous reported cases of patient affected by
OTOF mutations.
P12.053
DFNB1 locus mutation analysis in Latvian patients with
nonsyndromic sensorineural hearing loss
O. Sterna 1,2 , I. Grinfelde 1 , N. Pronina 1 , D. Bauze 1 , Z. Krumina 1 , L. Kornejeva 1 ,
B. Lace 1 , S. Kuske 3 , R. Lugovska 1 ;
1 Medical Genetics clinic, University Children’s Hospital, Riga, Latvia, 2 Rigas
Stradins University, Riga, Latvia, 3 Latvian Childrens` Hearing centre, Riga,
Latvia.
Background: Hearing loss is the most common birth defect and the
most prevalent sensorineural disorder in developed countries. More
than half of prelingual deafness cases are due to genetic factors.
About 70% of all hereditary deafness cases are classified as nonsyndromic
and recessive.
Approximately 50% of autosomal recessive nonsyndromic hearing
loss can be attributed to the disorder DFNB1, caused by mutations in
the genes GJB2 and GJB6 (which encode proteins connexin 26 and
connexin 30). DFNB1 has digenic pattern of inheritance. The 35delG
mutation in GJB2 gene is the most common mutation in DNFB1 in
many populations.
Materials: We obtained 151 DNA samples from patients with prelingual
hearing loss in whom syndromic forms and environmental causes of
deafness had been excluded, their relatives and individuals with hearing
loss positive family history.
Methods: DNA was extracted from whole blood. The GJB2 exon 2
analysis was performed using PCR, enzymatic restriction and automated
sequencing. Analysis of del(GJB6-D13S1830) and del(GJB6-
D13S1854) in GJB6 was performed by multiplex-PCR.
Results: 65 unrelated patients were screened for the GJB2 mutations.
Four different mutations in the GJB2 gene have been identified in Latvian
DFNB1 patients: 35delG, 311-324del14, 235delC and M34T. One
heterozygous 51del12insA mutation was detected in unaffected individual
with positive family history.
Two causative GJB2 mutations were found in 37 patients (56%), 25
patients had no GJB2 mutations, three patients are heterozygous for
one GJB2 mutation and the cause of impairment remains unclear.
We have started testing for two GJB6 deletions and the results are in
process.
P12.054
Identification of a novel mutation in RPS19 in a patient with
Diamond-Blackfan anemia
M. Kurnikova 1 , M. Maschan 2 , I. Kalinina 2 , D. Shagin 1,3 ;
1 Evrogen Joint Stock Company, Moscow, Russian Federation, 2 Federal Research
Clinical Center for pediatric hematology, oncology and immunology,
Moscow, Russia, Moscow, Russian Federation, 3 Shemyakin and Ovchinnikov
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