Jutta Wirth

Mouse Dac, a novel nuclear factor with homology to Drosophila dachshund shows a dynamic expression in the neural crest, the eye, the neocortex, and the limb bud

Dac is a novel nuclear factor in mouse and humans that shares homology with Drosophila dachshund (dac). Alignment with available sequences defines a conserved box of 117 amino acids that shares weak homology with the proto‐oncogene Ski and Sno. Dac expression is found in various neuroectodermal and mesenchymal tissues. At early developmental stages Dac is expressed in lateral mesoderm and in neural crest cells. In the neural plate/tube Dac expression is initially seen in the prosencephalon and gets gradually restricted to the presumptive neocortex and the distal portion of the outgrowing optic vesicle. Furthermore, Dac transcripts are detected in the mesenchyme underlying the Apical Ectodermal Ridge (AER) of the extending limb bud, the dorsal root ganglia and chain ganglia, and the mesenchyme of the growing genitalia. Dac expression in the Gli 3 mutant extra toes (Xt/Xt) shows little difference compared to the expression in wild‐type limb buds. In contrast, a significant expansion of Dac expression are observed in the anterior mesenchyme of the limb buds of hemimelic extra toes (Hx/+) mice. FISH analysis reveals that human DAC maps to chromosome 13q22.3–23 and further fine‐mapping defined a position of the DAC gene at 54cM or 13q21.1, a locus that associates with mental retardation and skeletal abnormalities. Dev Dyn 1999;214:66–80.

High resolution comparative genomic hybridisation analysis reveals imbalances in dyschromosomal patients with normal or apparently balanced conventional karyotypes.

A sensitive technique is needed for screening whole genome imbalances in dyschromosomal patients when G-banding shows normal karyotypes or apparently balanced translocations. In this study we performed highly sensitive comparative genomic hybridisation analysis on a number of such cases and revealed chromosomal imbalances in all.

Complex FISH probes for the subtelomeric regions of all human chromosomes: comparative hybridization of CEPH YACs to chromosomes of the Old World monkey Presbytis cristata and great apes

We have generated a human subtelomere probe panel, utilizing well characterized CEPH YACs, for the investigation of human chromosome pathology and evolution through fluorescent in situ hybridization (FISH). Region-specific FISH probes will be extremely valuable for detecting cytogenetically cryptic telomere abnormalities. Here, we present the first comparative mapping study (with 29 subtelomere probes and 6 chromosome paints) to the Old World monkey Presbytis cristata, followed by hybridizations to the great apes, gorilla and orangutan, when rearrangements were detected. We observed that the position of telomere-associated genomic sequences has been only moderately conserved during primate evolution. YAC 364f9, specific for the subtelomeric long arm of human chromosome 3, contains an evolutionary inversion breakpoint that was involved in independent chromosome rearrangements in P. cristata and gorilla.

Mild phenotype in two unrelated patients with a partial deletion of 21q22.2-q22.3 defined by FISH and molecular studies

We describe two unrelated patients with cytogenetically visible deletions of 21q22.2‐q22.3 and mild phenotypes. Both patients presented minor dysmorphic features including thin marfanoid build, facial asymmetry, downward‐slanting palpebral fissures, depressed nasal bridge, small nose with bulbous tip, and mild mental retardation (MR). FISH and molecular studies indicated common deleted areas but different breakpoints. In patient 1, the breakpoint was fine mapped to a 5.2 kb interval between exon 5 and exon 8 of the ETS2 gene. The subtelomeric FISH probe was absent on one homologue 21 indicating a terminal deletion spanning ∼7.9 Mb in size. In patient 2, the proximal breakpoint was determined to be 300–700 kb distal to ETS2, and the distal breakpoint 2.5–0.3 Mb from the 21q telomere, indicating an interstitial deletion sized ∼4.7–7.3 Mb. The 21q‐ syndrome is rare and typically associated with a severe phenotype, but different outcomes depending on the size and location of the deleted area have been reported. Our data show that monosomy 21q of the area distal to the ETS2 gene, representing the terminal 7.9 Mb of 21q, may result in mild phenotypes comprising facial anomalies, thin marfanoid build, and mild MR, with or without signs of holoprosencephaly.

Molecular cytogenetic characterisation of a complex 46,XY,t(7;8;11;13) chromosome rearrangement in a patient with Moebius syndrome

Editor—Carriers of de novo balanced reciprocal translocations and inversions have an increased risk of approximately 6% for developing multiple congenital abnormalities (MCA) and/or mental retardation (MR), compared to a 2-3% risk overall in newborn populations.1 2 Cytogenetically cryptic deletions or physical disruption or inactivation of a gene(s) in one or both breakpoint regions may account for the observed phenotypes.3 4 It seems plausible to assume that the risk for MCA/MR may be even higher in carriers of de novo complex chromosome rearrangements (CCRs), which involve at least three different chromosomes and breakpoint regions. Extreme cases involving up to seven chromosomes and 10 breakpoints have been described.5-7Indeed, most reported CCRs are associated with MCA/MR.8 9In addition, they have been found in infertile men10 and in women suffering from multiple miscarriages.11 12 The complex nature of CCRs renders karyotype interpretation by classical chromosome banding alone difficult. In many cases fluorescence in situ hybridisation (FISH) will be the best method to delineate the underlying chromosome rearrangements.7 13Here we have applied conventional FISH with chromosome painting probes and region specific large insert clones, comparative genomic hybridisation (CGH),14 15 and spectral karyotyping (SKY)16 17 to an apparently balanced and very complex rearrangement in a profoundly retarded patient with Moebius syndrome (MBS, MIM 157900).18 MBS is characterised by congenital paralysis of the seventh cranial nerve leading to facial diplegia.19 Other cranial nerves may also be affected. In addition, orofacial and limb malformations, defects of the musculoskeletal system, and MR may occur. This patient, who has classical Moebius syndrome, has been reported previously.4 He was the third child born to a 35 year old father and a 32 year old mother. Because of paresis of the facial muscles as a …

A somatic cell hybrid panel for distal 17q: GDIA1 maps to 17q25.3.

A somatic cell hybrid panel was constructed consisting of seven hybrids with translocation breakpoints spanning the region 17q23-->q25. Hybrid clones carrying the longarm derivative of chromosome 17 in the absence of the normal chromosome 17 and of the derivative 17 were initially identified by PCR typing for a proximal and distal 17q marker. The translocation breakpoints of the hybrids were then mapped in more detail by PCR analysis for a number of microsatellite markers from chromosome 17q as well as for five gene loci (CACNLG, GH1, SOX9, TIMP2, TK1) previously mapped to the region 17q23-->q25. In addition, the locus for GDIA1 was mapped by FISH to 17q25.3 and fine mapped with the help of the hybrid panel. These seven new hybrids complement the existing somatic cell hybrid panel for the long arm of chromosome 17q.

Constitutional de novo interstitial deletion of 8 Mb on chromosome 22q12.1-12.3 encompassing the neurofibromatosis type 2 (NF2) locus in a dysmorphic girl with severe malformations

We report on the cytogenetic and molecular characterisation of a constitutional de novo interstitial deletion of chromosome 22q12.1-q12.3 in a dysmorphic girl. The deletion extends over approximately 8 Mb including the NF2 gene region. The corresponding deletion syndrome is characterised by severe developmental delay accompanied by multiple malformations at an age when clinical manifestation of NF2 is not expected. The proband is the second daughter of a 28 year old, gravida 2, para 2 woman and her unrelated 35 year old husband. The pregnancy was uncomplicated until 30 weeks, when polyhydramnios and congenital heart disease were diagnosed by ultrasonography. Because of these abnormalities, karyotype analysis was performed on fetal blood obtained by percutaneous umbilical cord blood sampling. Spontaneous delivery occurred at 31 weeks of gestation after premature labour (birth weight 1360 g, 25th centile; length 41.5 cm, 50th centile; OFC 29.8 cm, 75th centile). Dysmorphic features (fig 1) consisting of depressed nasal root, hypertelorism, small and downward slanting palpebral fissures, short philtrum with a tented upper lip, mandibular hypoplasia, low set, and posteriorly rotated ears, overlapping fingers and toes, and a large cleft palate were noted. The child presented with visceral situs inversus with dextrocardia, interrupted aortic arch type A, a large ventricular septal defect, subaortic stenosis secondary to conoventricular malalignment, hypoplastic ascending aorta, and bilateral superior caval veins with drainage of the right sided caval vein via a coronary sinus into the right atrium. Prostaglandin E1 infusion was given to maintain ductal patency until the age of 4 months when surgical repair of the aortic arch abnormality and subaortic stenosis was done. Furthermore, duodenal stenosis with annular pancreas were detected requiring surgical intervention at the age of 1 week. Cranial ultrasound showed a congenital malformation of the central nervous system with dilated, abnormally shaped lateral and third ventricles, …

Molecular cytogenetic analysis of a de novo balanced X;autosome translocation: Evidence for predominant inactivation of the derivative X chromosome in a girl with multiple malformations.

We report on the characterization of a de novo, apparently balanced translocation t(X;15)(p11.3;q26) detected in a girl with multiple congenital malformations. Replication banding studies on Epstein–Barr virus transformed peripheral blood lymphocytes revealed non‐random X chromosome inactivation with predominant inactivation of the derivative X chromosome. Using chromosomal fluorescence in situ hybridization (FISH), we located the breakpoints to a 30 kb region on the short arm of the X chromosome band p11.3 and to a 160 kb region defined by BAC RP11‐89K11 on the long arm of chromosome 15. Our data suggest that the disruption/disturbance of plant homeo domain (PHD) zinc finger gene KIAA0215 or of another gene (RGN, RNU12, P17.3, or RBM10) in the breakpoint region on the X chromosome is not well tolerated and leads to the selection of cells with an active non‐rearranged X chromosome.

Early onset, non-progressive, mild cerebellar ataxia co-segregating with a familial balanced translocation t(8;20)(p22;q13)

Hereditary ataxia is a clinically and genetically heterogenous group of disorders. Most are progressive and associated with other neurological abnormalities. Early onset, non-progressive cerebellar ataxia (OMIM #117360) has been described as a dominantly inherited disorder associated with isolated vermal atrophy1–3 or generalised atrophy of the cerebellum.4,5 This is a rare entity compared with autosomal recessive early onset cerebellar ataxia with retained tendon reflexes (OMIM #212895).6 Various disease genes have been identified using rare disease associated balanced chromosomal rearrangements (DBCRs), for example, translocations or inversions that truncate, delete, or otherwise inactivate genes.7 DBCRs may occur in at least 1% of patients with autosomal dominant disorders caused by haploinsufficiency, and in many girls affected by X linked recessive disorders. During a systematic search for apparently balanced chromosomal rearrangements associated with abnormal phenotypes,7 we identified a four generation family in which a variable neurological phenotype including an early onset, non-progressive, and mild cerebellar ataxia segregates together with a balanced reciprocal translocation. ### Family history The study was approved by the local ethics committee (no. 1992–2489). The family consists of four generations as shown in fig 1. All family members, except II:2, were personally interviewed and underwent neurological examination by one of us (BS). The affected members in generations III, IV, and V have developed a phenotype of clumsiness starting in early childhood (1–7 years), including gait abnormalities with lurching and frequent falling, which increased upon physical activity. Objective findings included ataxia, dysmetria on finger to nose and/or heel to shin test, tremor, nystagmus, and retained reflexes in the lower limbs. Neurological symptoms and the phenotype of the affected members are presented in table 1. MRI of two of the patients (III:2 and III:4) performed at 49 and 43 years of age, respectively, gave inconclusive results. Anticipation was not observed …

Girl with phenotypic abnormalities and a de novo, apparently balanced translocation 46,XX,t(5;10)(q35.2q11.2)

We describe a three-year-old girl with a triangular face, epicanthus, midfacial hypoplasia, apparently low-set ears, a small mouth with thin vermilion border, and a small chin, hypermobile joints, developmental delay with insecure gait, dystonic movement disorder, speech defect, and a history of unexplained undernutrition. She has a de novo, apparently balanced translocation t(5;10)(q35.2;q11.2). Using fluorescence in situ hybridization (FISH), we located the breakpoints in the 1.5-Mb area defined by YAC 753f5 (5q35.2) and within the approximately 2-Mb interval between 10cen and YAC 933a3 (10q11.21).