Julie Steffann

Université Paris Descartes, Lutetia Parisorum, Île-de-France, France

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Publications (57)209.11 Total impact

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    ABSTRACT: Incontinentia pigmenti (IP) is an X-linked-dominant Mendelian disorder caused by mutation in the IKBKG/NEMO gene, encoding for NEMO/IKKgamma, a regulatory protein of nuclear factor kappaB (NF-kB) signaling. In more than 80% of cases, IP is due to recurrent or nonrecurrent deletions causing loss-of-function (LoF) of NEMO/IKKgamma. We review how the local architecture of the IKBKG/NEMO locus with segmental duplication and a high frequency of repetitive elements favor de novo aberrant recombination through different mechanisms producing genomic microdeletion. We report here a new microindel (c.436_471delinsT, p.Val146X) arising through a DNA-replication-repair fork-stalling-and-template-switching and microhomology-mediated-end-joining mechanism in a sporadic IP case. The LoF mutations of IKBKG/NEMO leading to IP include small insertions/deletions (indel) causing frameshift and premature stop codons, which account for 10% of cases. We here present 21 point mutations previously unreported, which further extend the spectrum of pathologic variants: 14/21 predict LoF because of premature stop codon (6/14) or frameshift (8/14), whereas 7/21 predict a partial loss of NEMO/IKKgamma activity (two splicing and five missense). We review how the analysis of IP-associated IKBKG/NEMO hypomorphic mutants has contributed to the understanding of the pathophysiological mechanism of IP disease and has provided important information on affected NF-kB signaling. We built a locus-specific database listing all IKBKG/NEMO variants, accessible at http://IKBKG.lovd.nl.
    Human Mutation 11/2013; · 5.21 Impact Factor
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    ABSTRACT: PCR amplification on single cells is prone to allele drop-out (PCR failure of one allele), a cause of misdiagnosis in preimplantation genetic diagnosis (PGD). Owing to this error risk, PGD usually relies on both direct and indirect genetic analyses. When the affected partner is the sporadic case of a dominant disorder, building haplotypes require spermatozoon or polar body testing prior to PGD, but these procedures are cost and time-consuming. A couple requested PGD because the male partner suffered from a dominant Cowden syndrome (CS). He was a sporadic case, but the couple had a first unaffected child and the non-mutated paternal haplotype was tentatively deduced. The couple had a second spontaneous pregnancy and the fetus was found to carry the at-risk haplotype but not the PTEN mutation. The mutation was present in blood from the affected father, but at low level, confirming the somatic mosaicism. Ignoring the possibility of mosaicism in the CS patient would have potentially led to selection of affected embryos. This observation emphasizes the risk of PGD in families at risk to transmit autosomal-dominant disorder when the affected partner is a sporadic case.European Journal of Human Genetics advance online publication, 11 September 2013; doi:10.1038/ejhg.2013.164.
    European journal of human genetics: EJHG 09/2013; · 3.56 Impact Factor
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    ABSTRACT: Mitochondrial DNA (mtDNA) content is thought to remain stable over the preimplantation period of human embryogenesis, that is therefore suggested to be entirely dependent on ooplasm mtDNA capital. We have explored the impact of two disease-causing mutations (m.3243A>G MELAS and m.8344A>G MERRF) on mtDNA amounts in human oocytes and day4-5 preimplantation embryos. The mtDNA amount was stable in MERRF and control materials, while gradually increasing from the germinal vesicle of oogenesis to the blastocyst stage of embryogenesis in MELAS cells, MELAS embryos carrying ∼3-fold higher mtDNA amount than control embryos (p=0.0003). A correlation between mtDNA copy numbers and mutant loads was observed in MELAS embryos (R(2)=0.42, p<0.0013), suggestive of a compensation for the respiratory chain defect resulting from high mutation levels. These results suggest that mtDNA can replicate in early embryos and emphasize the need for sufficient amount of wild-type mtDNA to sustain embryonic development in humans.
    Human Molecular Genetics 02/2013; · 7.69 Impact Factor
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    ABSTRACT: BACKGROUND: The high frequency of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) gene mutation p.Arg117His in patients with congenital bilateral absence of the vas deferens (CBAVD) and in newborns screened for CF has created a dilemma. METHODS: Phenotypic and genotypic data were retrospectively collected in 179 non-newborn French individuals carrying p.Arg117His and a second CFTR mutation referred for symptoms or family history, by all French molecular genetics laboratories, referring physicians, CF care centres and infertility clinics. RESULTS: 97% of the patients had the intronic T7 normal variant in cis with p.Arg117His. 89% patients were male, with CBAVD being the reason for referral in 76%. In 166/179 patients with available detailed clinical features, final diagnoses were: four late-onset marked pulmonary disease, 83 isolated CBAVD, 67 other CFTR-related phenotypes, including 44 CBAVD with pulmonary and/or pancreatic symptoms and 12 asymptomatic cases. Respiratory symptoms were observed in 30% of the patients, but the overall phenotype was mild. No correlation was observed between sweat chloride concentrations and disease severity. Five couples at risk of CF offspring were identified and four benefited from prenatal or preimplantation genetic diagnoses (PND or PGD). Eight children were born, including four who were compound heterozygous for p.Arg117His and one with a severe CF mutation. CONCLUSIONS: Patients with CBAVD carrying p.Arg117His and a severe CF mutation should benefit from a clinical evaluation and follow-up. Depending on the CBAVD patients' genotype, a CFTR analysis should be considered in their partners in order to identify CF carrier couples and offer PND or PGD.
    Journal of Medical Genetics 02/2013; · 5.70 Impact Factor
  • European journal of human genetics: EJHG 10/2012; · 3.56 Impact Factor
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    European Respiratory Journal 06/2012; 39(6):1534-5. · 6.36 Impact Factor
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    ABSTRACT: Isolated complex I deficiency is a frequent cause of respiratory chain defects in childhood. In this study, we report our systematic approach with blue native PAGE (BN-PAGE) to study mitochondrial respiratory chain assembly in skin fibroblasts from patients with Leigh syndrome and CI deficiency. We describe five new NDUFS4 patients with a similar and constant abnormal BN-PAGE profile and present a meta-analysis of the literature. All NDUFS4 mutations that have been tested with BN-PAGE result in a constant and similar abnormal assembly profile with a complete loss of the fully assembled complex I usually due to a truncated protein and the loss of its canonical cAMP dependent protein kinase phosphorylation consensus site. We also report the association of abnormal brain MRI images with this characteristic BN-PAGE profile as the hallmarks of NDUFS4 mutations and the first founder NDUFS4 mutations in the North-African population.
    Biochimica et Biophysica Acta 02/2012; 1822(6):1062-9. · 4.66 Impact Factor
  • Clinical Genetics 10/2011; 80(4):403-5. · 4.25 Impact Factor
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    ABSTRACT: Preimplantation genetic diagnosis (PGD) is authorized in France since 1999. After 10 years, technical results are encouraging. With the development of new technologies, our team is able to diagnosis the large majority of chromosome translocations and 75 monogenic diseases. However, PGD remains limited because of the growing augmentation of demands causing an increasing delay for the first procedure of more than 18 months. Since 2006, 19 couples asked for a PGD with HLA typing. In January 2011, 11 couples have already been included in our PGD program. The birth of the first child after PGD with HLA typing offers new perspectives of treatment for these couples.
    Journal de Gynécologie Obstétrique et Biologie de la Reproduction 09/2011; 40(7):682-6. · 0.45 Impact Factor
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    ABSTRACT: Because the mtDNA amount remains stable in the early embryo until uterine implantation, early human development is completely dependent on the mtDNA pool of the mature oocyte. Both quantitative and qualitative mtDNA defects therefore may negatively impact oocyte competence or early embryonic development. However, nothing is known about segregation of mutant and wild-type mtDNA molecules during human meiosis. To investigate this point, we compared the mutant levels in 51 first polar bodies (PBs) and their counterpart (oocytes, blastomeres, or whole embryos), at risk of having (1) the "MELAS" m.3243A>G mutation in MT-TL1 (n = 30), (2) the "MERRF" m.8344A>G mutation in MT-TK (n = 15), and (3) the m.9185T>G mutation located in MT-ATP6 (n = 6). Seven out of 51 of the PBs were mutation free and had homoplasmic wild-type counterparts. In the heteroplasmic PBs, measurement of the mutant load was a rough estimate of the counterpart mutation level (R(2) = 0.52), and high mutant-load differentials between the two populations were occasionally observed (ranging from -34% to +34%). The mutant-load differentials between the PB and its counterpart were higher in highly mutated PBs, suggestive of a selection process acting against highly mutated cells during gametogenesis or early embryonic development. Finally, individual discrepancies in mutant loads between PBs and their counterparts make PB-based preconception diagnosis unreliable for the prevention of mtDNA disorder transmission. Such differences were not observed in animal models, and they emphasize the need to conduct thorough studies on mtDNA segregation in humans.
    The American Journal of Human Genetics 04/2011; 88(4):494-8. · 11.20 Impact Factor
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    ABSTRACT: Mitochondrial DNA (mtDNA) mutations cause a wide range of serious diseases with high transmission risk and maternal inheritance. Tissue heterogeneity of the heteroplasmy rate ("mutant load") accounts for the wide phenotypic spectrum observed in carriers. Owing to the absence of therapy, couples at risk to transmit such disorders commonly ask for prenatal (PND) or preimplantation diagnosis (PGD). The lack of data regarding heteroplasmy distribution throughout intrauterine development, however, hampers the implementation of such procedures. We tracked the segregation of the m.3243A>G mutation (MT-TL1 gene) responsible for the MELAS syndrome in the developing embryo/fetus, using tissues and cells from eight carrier females, their 38 embryos and 12 fetuses. Mutant mtDNA segregation was found to be governed by random genetic drift, during oogenesis and somatic tissue development. The size of the bottleneck operating for m.3243A>G during oogenesis was shown to be individual-dependent. Comparison with data we achieved for the m.8993T>G mutation (MT-ATP6 gene), responsible for the NARP/Leigh syndrome, indicates that these mutations differentially influence mtDNA segregation during oogenesis, while their impact is similar in developing somatic tissues. These data have major consequences for PND and PGD procedures in mtDNA inherited disorders.
    Human Mutation 01/2011; 32(1):116-25. · 5.21 Impact Factor
  • Medecine sciences: M/S 11/2010; 26(11):897-9. · 0.56 Impact Factor
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    ABSTRACT: To identify a consistent pattern of brain MRI imaging in primary complex I deficiency. Complex I deficiency, a major cause of respiratory chain dysfunction, accounts for various clinical presentations, including Leigh syndrome. Human complex I comprises seven core subunits encoded by mitochondrial DNA (mtDNA) and 38 core subunits encoded by nuclear DNA (nDNA). Moreover, its assembly requires six known and many unknown assembly factors. To date, no correlation between genotypes and brain MRI phenotypes has been found in complex I deficiencies. The brain MRIs of 30 patients carrying known mutation(s) in genes involved in complex I were retrospectively collected and compared with the brain MRIs of 11 patients carrying known mutations in genes involved in the pyruvate dehydrogenase (PDH) complex as well as 10 patients with MT-TL1 mutations. All complex I deficient patients showed bilateral brainstem lesions (30/30) and 77% (23/30) showed anomalies of the putamen. Supratentorial stroke-like lesions were only observed in complex I deficient patients carrying mtDNA mutations (8/19) and necrotising leucoencephalopathy in patients with nDNA mutations (4/5). Conversely, the isolated stroke-like images observed in patients with MT-TL1 mutations, or the corpus callosum malformations observed in PDH deficient patients, were never observed in complex I deficient patients. A common pattern of brain MRI imaging was identified with abnormal signal intensities in brainstem and subtentorial nuclei with lactate peak as a clue of complex I deficiency. Combining clinico-biochemical data with brain imaging may therefore help orient genetic studies in complex I deficiency.
    Journal of Medical Genetics 10/2010; 48(1):16-23. · 5.70 Impact Factor
  • J Steffann, C Fallet
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    ABSTRACT: Mitochondria play a central role in cellular energy metabolism. Mitochondrial genome (mtDNA) is specific with a maternal transmission. Defects of mtDNA, both quantitative (depletion) but also qualitative (mutation) were observed in patients with reproductive disorders, suggesting that a mitochondrial deficit could cause a failure of oocyte maturation. In our experience, some mtDNA point mutations would be subject to negative selection during female gametogenesis, with a threshold rate depending on the mutation. Below this threshold, the presence of mtDNA mutations would not impact oocyte maturation nor early embryonic development, as evidenced by the large number of oocytes and embryos carrying high mutation rates in our series.
    Journal de Gynécologie Obstétrique et Biologie de la Reproduction 04/2010; 39(1 Suppl):11-3. · 0.45 Impact Factor
  • J. Steffann, C. Fallet
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    ABSTRACT: Mitochondria play a central role in cellular energy metabolism. Mitochondrial genome (mtDNA) is specific with a maternal transmission. Defects of mtDNA, both quantitative (depletion) but also qualitative (mutation) were observed in patients with reproductive disorders, suggesting that a mitochondrial deficit could cause a failure of oocyte maturation. In our experience, some mtDNA point mutations would be subject to negative selection during female gametogenesis, with a threshold rate depending on the mutation. Below this threshold, the presence of mtDNA mutations would not impact oocyte maturation nor early embryonic development, as evidenced by the large number of oocytes and embryos carrying high mutation rates in our series.
    Journal De Gynecologie Obstetrique Et Biologie De La Reproduction - J GYNECOL OBSTET BIOL REPROD. 01/2010; 39(1):11-13.
  • Reproductive Biomedicine Online - REPROD BIOMED ONLINE. 01/2010; 20.
  • Reproductive Biomedicine Online - REPROD BIOMED ONLINE. 01/2010; 20.
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    ABSTRACT: With the detection of a homozygous deletion of the survival motor neuron 1 gene (SMN1), prenatal and preimplantation genetic diagnosis (PGD) for spinal muscular atrophy has become feasible and widely applied. The finding of a de novo rearrangement, resulting in the loss of the SMN1 gene, reduces the recurrence risk from 25% to a lower percentage, the residual risk arising from recurrent de novo mutation or germline mosaicism. In a couple referred to our PGD center because their first child was affected with SMA, the male partner was shown to carry two SMN1 copies. An analysis of the SMN1 gene and two flanking markers was performed on 12 single spermatozoa, to determine whether the father carried a CIS duplication of the SMN1 gene on one chromosome and was a carrier, or if the deletion has occurred de novo. We showed that all spermatozoa that were carriers of the 'at-risk haplotype' were deleted for the SMN1 gene, confirming the carrier status of the father. We provide an original application of single germ cell studies to recessive disorders using coamplification of the gene and its linked markers. This efficient and easy procedure might be useful to elucidate complex genetic situations when samples from other family members are not available.
    European journal of human genetics: EJHG 11/2009; 18(4):505-8. · 3.56 Impact Factor
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    ABSTRACT: Preimplantation genetic diagnosis (PGD) is used to analyze embryos genetically before their transfer into the uterus. It was developed first in England in 1990, as part of progress in reproductive medicine, genetic and molecular biology. PGD offers couples at risk the chance to have an unaffected child, without facing termination of pregnancy. Embryos are obtained by in vitro fertilization with intracytoplasmic sperm injection (ICSI), and are biopsied mostly on day 3; blastocyst biopsy is mentioned as a possible alternative. The genetic analysis is performed on one or two blastomeres, by fluorescent in situ hybridization (FISH) for cytogenetic diagnosis, or polymerase chain reaction (PCR) for molecular diagnosis. Genetic analysis of the first or second polar body can be used to study maternal genetic contribution. Only unaffected embryos are transferred into the uterus. To improve the accuracy of the diagnosis, new technologies are emerging, with comparative genomic hybridization (CGH) and microarrays. In Europe, depending on national regulations, PGD is either prohibited, or allowed, or practiced in the absence of recommendations. The indications are chromosomal abnormalities, X-linked diseases or single gene disorders. The number of disorders being tested increases. In Europe, data collection from the year 2004 reports that globally 69.6% of cycles lead to embryo transfer and implantation rate is 17%. European results from the year 2004 show a clinical pregnancy rate of 18% per oocyte retrieval and 25% per embryo transfer, leading to 528 babies born. The cohort studies concerning the paediatric follow-up of PGD babies show developmental outcomes similar to children conceived after IVF-ICSI. Recent advances include human leucocyte antigen (HLA) typing for PGD embryos, when an elder sibling is affected with a genetic disorder and needs stem cell transplantation. The HLA-matched offspring resulting can give cord blood at birth. Preimplantation genetic screening (PGS) consists in euploid embryo selection; it could be used for advanced maternal age, repeated implantation failure, single embryo transfer or idiopathic recurrent pregnancy loss. These applications are controversial. PGD for inherited cancer predispositions is discussed and social sexing remains prohibited in Europe. PGD requires a close collaboration between obstetricians, fertility specialists, IVF laboratory and human geneticists. It needs intensive effort, expensive techniques and is demanding for the patients, but it offers tremendous opportunity for couples whose previous child has exhibited genetic abnormalities. The debate on certain indications is ongoing.
    European journal of obstetrics, gynecology, and reproductive biology 06/2009; 145(1):9-13. · 1.97 Impact Factor

Publication Stats

657 Citations
286 Downloads
3k Views
209.11 Total Impact Points

Institutions

  • 2006–2013
    • Université Paris Descartes
      • Faculté de Médecine
      Lutetia Parisorum, Île-de-France, France
  • 2005–2013
    • Université René Descartes - Paris 5
      • Faculté de Médecine
      Paris, Ile-de-France, France
    • Hôpital Universitaire Necker
      Lutetia Parisorum, Île-de-France, France