Detlef Böhm

Targeted next generation sequencing as a diagnostic tool in epileptic disorders

Purpose:  Epilepsies have a highly heterogeneous background with a strong genetic contribution. The variety of unspecific and overlapping syndromic and nonsyndromic phenotypes often hampers a clear clinical diagnosis and prevents straightforward genetic testing. Knowing the genetic basis of a patient’s epilepsy can be valuable not only for diagnosis but also for guiding treatment and estimating recurrence risks.

Haploinsufficiency of a Spliceosomal GTPase Encoded by EFTUD2 Causes Mandibulofacial Dysostosis with Microcephaly

Mandibulofacial dysostosis with microcephaly (MFDM) is a rare sporadic syndrome comprising craniofacial malformations, microcephaly, developmental delay, and a recognizable dysmorphic appearance. Major sequelae, including choanal atresia, sensorineural hearing loss, and cleft palate, each occur in a significant proportion of affected individuals. We present detailed clinical findings in 12 unrelated individuals with MFDM; these 12 individuals compose the largest reported cohort to date. To define the etiology of MFDM, we employed whole-exome sequencing of four unrelated affected individuals and identified heterozygous mutations or deletions of EFTUD2 in all four. Validation studies of eight additional individuals with MFDM demonstrated causative EFTUD2 mutations in all affected individuals tested. A range of EFTUD2-mutation types, including null alleles and frameshifts, is seen in MFDM, consistent with haploinsufficiency; segregation is de novo in all cases assessed to date. U5-116kD, the protein encoded by EFTUD2, is a highly conserved spliceosomal GTPase with a central regulatory role in catalytic splicing and post-splicing-complex disassembly. MFDM is the first multiple-malformation syndrome attributed to a defect of the major spliceosome. Our findings significantly extend the range of reported spliceosomal phenotypes in humans and pave the way for further investigation in related conditions such as Treacher Collins syndrome.

Disruption of PLC-beta 1-mediated signal transduction in mutant mice causes age-dependent hippocampal mossy fiber sprouting and neurodegeneration.

Aberrant reorganization of hippocampal mossy fibers occurs in human temporal lobe epilepsy and rodent epilepsy models. We generated a mouse model showing massive late-onset aberrant mossy fiber sprouting in the adult hippocampus. The mutation in this mouse model derives from an intronic insertion of transgene DNA in the mouse PLC-beta1 gene (PLC-beta 1(-/-)(TC) mutation) leading to a splice mutation of the PLC-beta 1 gene and a complete loss of downstream PLC-beta 1 expression. PLC-beta 1(-/-)(TC) mutants develop a loss of NMDA-receptors in the stratum oriens of region CA1, apoptotic neuronal death, and reduced hippocampal PKC activity. The phenotype of these mice further consists of a late-onset epileptiform hyperexcitability, behavioral modifications in a radial maze and in an open field, female nurturing defect, and male infertility. In the present study, we provide evidence that the arising of the behavioral phenotype in PLC-beta 1(-/-)(TC) mice correlates in time with the development of the aberrant mossy fiber projections and that the disruption of the PLC-beta 1-mediated signal transduction pathway may lead to a functional cholinergic denervation, which could cause hippocampal remodeling and, in consequence, epileptiform hyperexcitability.

Array CGH in molecular diagnosis of mental retardation - A study of 150 Finnish patients.

We report on the results of an array comparative genomic hybridization (array CGH) study of 150 karyotypically normal Finnish patients with idiopathic mental retardation and/or dysmorphic features and/or malformations. Using high‐resolution microarray analysis, we sought to identify clinically relevant microdeletions and microduplications in these patients. The results were confirmed using other methods and compared with findings reported in recent publications and internet databases. Small aberrations of potential clinical significance were found in 28 (18.6%) of the 150 patients. Eight of the identified aberrations are known to cause syndromes, 4 affected the X chromosome in males, 4 were familial, and 13 have yet to be associated with a phenotype. This study demonstrates the benefits of array CGH in clinical diagnostics of developmental disorders. Further, our findings give evidence of new syndromes.

An Emerging 1q21.1 Deletion-Associated Neurodevelopmental Phenotype

In this study, we describe the neurodevelopmental and epileptic phenotypes in a family with an inherited 1q21.1 deletion. During the pregnancy with the proband, increased nuchal translucency and oligohydramnion were detected. The proband showed mild global developmental delay and ataxic gait. Seizures started in the proband at the age of 2 years and manifested as generalized tonic—clonic seizures, atypical absence seizures, head drops, and drop attacks with no abnormal findings on interictal electroencephalogram. We performed an Agilent Human Genome CGH (comparative genomic hybridization) Microarray 105A, and a microdeletion on chromosome 1q21.1 was identified in both the patient and his asymptomatic father. This deletion encompasses 1.65 Mb and is larger than the reported recurrent class I deletions in this region. Cryptic cytogenetic abnormalities should be considered in patients with neurodevelopmental problems and atypical presentation of epilepsy with a normal electroencephalography (EEG).

Partial trisomy of distal 19q detected by quantitative real‐time PCR and FISH in a girl with mild facial dysmorphism, hypotonia and developmental delay

We report on a 2

First non-mosaic case of isopseudodicentric chromosome 18 (psu idic(18)(pter q22.1::q22.1 pter) Is associated with multiple congenital anomalies reminiscent of trisomy 18 and 18q− syndrome†

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TSPY Expression Is Variably Altered in Transgenic Mice with Testicular Feminization

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Rat transition nuclear protein 2 regulatory region directs haploid expression of reporter gene in male germ cells of transgenic mice

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Premature translation of transition protein 2 mRNA causes sperm abnormalities and male infertility

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