Sibylle Jakubiczka

Mutations of the ephrin-B1 gene cause craniofrontonasal syndrome.

Craniofrontonasal syndrome (CFNS) is an X-linked craniofacial disorder with an unusual manifestation pattern, in which affected females show multiple skeletal malformations, whereas the genetic defect causes no or only mild abnormalities in male carriers. Recently, we have mapped a gene for CFNS in the pericentromeric region of the X chromosome that contains the EFNB1 gene, which encodes the ephrin-B1 ligand for Eph receptors. Since Efnb1 mutant mice display a spectrum of malformations and an unusual inheritance reminiscent of CFNS, we analyzed the EFNB1 gene in three families with CFNS. In one family, a deletion of exons 2-5 was identified in an obligate carrier male, his mildly affected brother, and in the affected females. In the two other families, missense mutations in EFNB1 were detected that lead to amino acid exchanges P54L and T111I. Both mutations are located in multimerization and receptor-interaction motifs found within the ephrin-B1 extracellular domain. In all cases, mutations were found consistently in obligate male carriers, clinically affected males, and affected heterozygous females. We conclude that mutations in EFNB1 cause CFNS.

Sonography of the median nerve in CMT1A, CMT2A, CMTX, and HNPP

Introduction: In this study we compare the ultrasound features in the median nerve in patients with different types of Charcot–Marie–Tooth (CMT) disease and hereditary neuropathies with liability to pressure palsies (HNPP) as a typical entrapment neuropathy. Methods: Median nerve ultrasound and conduction studies were performed in patients with CMT1A (n = 12), MFN2‐associated CMT2A (n = 7), CMTX (n = 5), and HNPP (n = 5), and in controls (n = 28). Results: Median nerve cross‐sectional area (CSA) was significantly increased in CMT1A, whereas, in axonal CMT2A, fascicle diameter (FD) was enlarged. CSA correlated with nerve conduction slowing in CMT1A and with axonal loss, as shown by motor and sensory nerve amplitudes in both CMT1A and CMT2A. A relatively low wrist‐to‐forearm‐ratio (WFR <0.8) or a relatively high WFR (>1.8) appeared to be unlikely in MFN2 and Cx32 mutations of CMT2A and CMTX, respectively. Conclusion: Differences in CSA, FD, and WFR of the median nerve can be helpful in defining subtypes of hereditary neuropathies. Muscle Nerve 47:385‐395, 2013

Basal ganglia pathology in ALS is associated with neuropsychological deficits

Objectives: To evaluate basal ganglia changes along the amyotrophic lateral sclerosis (ALS)–ALS–frontotemporal dementia (FTD) continuum using multiple, complementary imaging techniques. Methods: Sixty-seven C9orf72-negative patients with ALS and 39 healthy controls were included in a cross-sectional quantitative MRI study. Seven patients with ALS met criteria for comorbid behavioral variant FTD (ALS-FTD), 18 patients met the Strong criteria for cognitive and/or behavioral impairment (ALS-Plus), and 42 patients had no cognitive impairment (ALS-Nci). Volumetric, shape, and density analyses were performed for the thalamus, amygdala, nucleus accumbens, hippocampus, caudate nucleus, pallidum, and putamen. Results: Significant basal ganglia volume differences were identified between the study groups. Shape analysis revealed distinct atrophy patterns in the amygdala in patients with ALS-Nci and in the hippocampus in patients with ALS-Plus in comparison with controls. Patients with ALS-FTD exhibited pathologic changes in the bilateral thalami, putamina, pallida, hippocampi, caudate, and accumbens nuclei in comparison with all other study groups. A preferential vulnerability has been identified within basal ganglia subregions, which connect directly to key cortical sites of ALS pathology. While the anatomical patterns were analogous, the degree of volumetric, shape, and density changes confirmed incremental pathology through the spectrum of ALS-Nci, ALS-Plus, to ALS-FTD. Performance on verbal memory tests correlated with hippocampal volumes, and accumbens nuclei volumes showed a negative correlation with apathy scores. Conclusions: We demonstrate correlations between basal ganglia measures and structure-specific neuropsychological performance and a gradient of incremental basal ganglia pathology across the ALS–ALS-FTD spectrum, suggesting that the degree of subcortical gray matter pathology in C9orf72-negative ALS is closely associated with neuropsychological changes.

Sex reversal in a child with the karyotype 46, XY, dup (1) (p22.3p32.3)

The karyotype 46,XY, dup(l) (p22.3p32.3) was found in a 10‐year‐old patient with sex reversal, mental retardation and multiple dysmorphic features. In other cases with duplication 1p but different breakpoints cryptorchidism and genital ambiguity have been observed suggesting the dosage effect of a locus in 1p involved in sex differentiation

Refinement of the deletion in 7q21.3 associated with split hand/foot malformation type 1 and Mondini dysplasia.

Split hand/foot malformation type I (SHFM1, OMIM *183600) is an autosomal dominant developmental disorder of limb formation that results in the absence of the central digital rays, deep median clefts, and syndactyly of the remaining digits. Patients with SHFM1 harbour deletions, translocations, and inversions in chromosomal region 7q21–q22.1 The deletions at 7q21–q22 encompass different genomic regions and probably result in a contiguous gene syndrome that includes growth impairment, microcephaly, craniofacial manifestations, hernias, hearing loss, and mental retardation.2,3 Cases with translocations do not show this broad pattern of abnormalities but are associated with hearing loss in most cases.4,5 Split hand/foot malformation type I is the only form of split hand/foot malformation associated with sensorineural hearing loss, and it has been designated SHFM1D (OMIM *605617).5,6 Recently, SHFM1D was shown to result from Mondini dysplasia in a boy with a de novo deletion of about 8.9–17 cM of the paternal chromosome 7q21.1–q21.3.7 So far, microdeletions at 7q21.3 have been described in only two cases: one in a boy with split hand/foot malformation plus mild mental retardation, growth retardation of post-natal onset, and hypotonia and another in a patient with ectrodactyly, ectodermal dysplasia, and cleft lip/palate (EEC) syndrome.8,9 Mapping of the deletion and translocation breakpoints in several patients showed a critical interval of about 1 Mb for the SHFM1 locus at 7q21.3.9 This interval included a 500 kb region that spanned five of seven known translocation breakpoints. In this region, the candidate genes DLX5 and DLX6 (human homologues of the Drosophila distal-less homeobox gene family) and DSS1 (deleted in the split hand/split foot SHFM1 region) were identified. No mutations were detected in patients with sporadic split hand/foot malformation with translocations or two families with split hand/foot malformation, sensorineural deafness, and normal chromosomes who …

Mice Lacking the Nuclear Pore Complex Protein ALADIN Show Female Infertility but Fail To Develop a Phenotype Resembling Human Triple A Syndrome

ABSTRACT Triple A syndrome is a human autosomal recessive disorder characterized by adrenal insufficiency, achalasia, alacrima, and neurological abnormalities affecting the central, peripheral, and autonomic nervous systems. In humans, this disease is caused by mutations in the AAAS gene, which encodes ALADIN, a protein that belongs to the family of WD-repeat proteins and localizes to nuclear pore complexes. To analyze the function of the gene in the context of the whole organism and in an attempt to obtain an animal model for human triple A syndrome, we generated mice lacking a functional Aaas gene. The Aaas −/− animals were found to be externally indistinguishable from their wild-type littermates, although their body weight was on the average lower than that of wild-type mice. Histological analysis of various tissues failed to reveal any differences between Aaas −/− and wild-type mice. Aaas −/− mice exhibit unexpectedly mild abnormal behavior and only minor neurological deficits. Our data show that the lack of ALADIN in mice does not lead to a triple A syndrome-like disease. Thus, in mice either the function of ALADIN differs from that in humans, its loss can be readily compensated for, or additional factors, such as environmental conditions or genetic modifiers, contribute to the disease.

Novel and Recurrent Mutations in Patients with Androgen Insensitivity Syndromes

Background/Aims: Androgen insensitivity syndrome (AIS) caused by mutations within the androgen receptor gene represents a variety of phenotypes from females with 46,XY karyotype over individuals with ambiguous genitalia to infertile males. Methods: We studied 24 patients with AIS by sequencing androgen receptor gene. 19 of the investigated patients were affected by complete androgen insensitivity syndrome (CAIS) and 5 suffered from partial androgen insensitivity syndrome (PAIS). Results: So far we have detected 12 unreported mutations as well as 9 recurrent mutations (3 recurrent mutations were detected twice) in exons 2–8 of the androgen receptor gene. Three of the novel mutations cause a frameshift with subsequent premature termination and were found in patients with CAIS. These frameshifts were induced by single nucleotide deletion or insertion, or in one case by a 13-bp deletion, respectively. Another premature stop codon found in a CAIS patient results from an already reported nucleotide substitution in exon 5. Furthermore, in a CAIS patient we found a novel duplication of codon 788. All other mutations caused single base substitutions spread through exons 2–8 and were associated with CAIS or PAIS. Conclusions: We report a broad spectrum of different mutations within the AR gene leading to various manifestations of AIS. Apart from truncating mutations, a reliable genotype/phenotype correlation cannot be established. Therefore, modifying factors must be effective.

Brain 1H magnetic resonance spectroscopic differences in myotonic dystrophy type 2 and type 1

To evaluate cerebral metabolism and intergroup differences in closely matched patients with myotonic dystrophy type 2 (DM2, n = 15) and type 1 (DM1, n = 14), we performed 1H magnetic resonance spectroscopic (MRS) analyses of the occipital and temporoparietal cortical regions as well as of subcortical frontal white matter. Relative to healthy subjects, the concentration of N‐acetylaspartate was significantly reduced in all tested brain regions in both disease groups. In the DM1 patients we also observed a concomitant depletion of creatine and choline levels, particularly in the frontal white matter. A discriminant analysis based on the 1H‐MRS data distinguished between the DM2, DM1, and control groups with an overall accuracy of 88%. 1H‐MRS indicates that neurochemical alterations involving gray and white matter occur in patients with DM2 and DM1. Although structural abnormalities (cerebral atrophy, white matter lesions) are similar in DM2 and DM1, changes in cerebral metabolites can differentiate these disease groups, suggesting that the diseases differ in their neurocellular pathology. Muscle Nerve, 2006

Neonatal progeria: increased ratio of progerin to lamin A leads to progeria of the newborn

Hutchinson–Gilford progeria syndrome (HGPS) is an important model disease for premature ageing. Affected children appear healthy at birth, but develop the first symptoms during their first year of life. They die at an average age of 13 years, mostly because of myocardial infarction or stroke. Classical progeria is caused by the heterozygous point mutation c.1824C>T in the LMNA gene, which activates a cryptic splice site. The affected protein cannot be processed correctly to mature lamin A, but is modified into a farnesylated protein truncated by 50 amino acids (progerin). Three more variations in LMNA result in the same mutant protein, but different grades of disease severity. We describe a patient with the heterozygous LMNA mutation c.1821G>A, leading to neonatal progeria with death in the first year of life. Intracellular lamin A was downregulated in the patients fibroblasts and the ratio of progerin to lamin A was increased when compared with HGPS. It is suggestive that the ratio of farnesylated protein to mature lamin A determines the disease severity in progeria.

Mapping of a further locus for X-linked craniofrontonasal syndrome

Craniofrontonasal syndrome is a rare dysostosis syndrome with an unusual pattern of X-linked inheritance, because males are usually not or less severely affected than females. Previously, a CFNS locus has been localised in Xp22. We report on a haplotype analysis in a German CFNS family, mapping the CFNS locus to the pericentromeric region of the X chromosome. This discrepancy can be explained by locus heter- ogeneity. Furthermore, random X inactivation could be demonstrated in affected females. The most plausible interpretation for this unusual pattern of X-linked inheritance is metabolic interference. Consequently, we propose that the CFNS gene escapes X inactivation.