Array based CGH and FISH fail to confirm duplication of 8p22-p23.1 in association with Kabuki syndrome.

BACKGROUND: Kabuki (Niikawa-Kuroki) syndrome comprises a characteristic facial appearance, cleft palate, congenital heart disease, and developmental delay. Various cytogenetically visible chromosomal rearrangements have been reported in single cases, but the molecular genetic basis of the condition has not been established. A recent report described a duplication of 8p22-p23.1 in 13/13 patients. OBJECTIVE: To determine the frequency of an 8p duplication in a cohort of patients with Kabuki syndrome. METHODS: An 8p duplication was sought using two independent methods--array based comparative genomic hybridisation (aCGH) and fluorescence in situ hybridisation (FISH)--in 15 patients with a definitive clinical diagnosis of Kabuki syndrome. RESULTS: No evidence for a duplication of 8p was obtained by FISH or aCGH in any of the 15 patients. CONCLUSIONS: 8p22-p23.1 duplication may not be a common mechanism for Kabuki syndrome. Another genetic abnormality may be responsible for the aetiology in many patients.

Molecular basis and characterization of the hyperinsulinism/hyperammonemia syndrome: predominance of mutations in exons 11 and 12 of the glutamate dehydrogenase gene. HI/HA Contributing Investigators.

Glutamate dehydrogenase (GDH) is allosterically activated by the amino acid leucine to mediate protein stimulation of insulin secretion. Children with the hyperinsulinism/hyperammonemia (HI/HA) syndrome have symptomatic hypoglycemia plus persistent elevations of plasma ammonium. We have reported that HI/HA may be caused by dominant mutations of GDH that lie in a unique allosteric domain that is encoded within GDH exons 11 and 12. To examine the frequency of mutations in this domain, we screened genomic DNA from 48 unrelated cases with the HI/HA syndrome for exon 11 and 12 mutations in GDH. Twenty-five (52%) had mutations in these exons; 74% of the mutations were sporadic. Clinical manifestations included normal birth weight, late onset of hypoglycemia, diazoxide responsiveness, and protein-sensitive hypoglycemia. Enzymatic studies of lymphoblast GDH in seven of the mutations showed that all had reduced sensitivity to inhibition with GTP, consistent with an increase in enzyme activity. Mutations had little or no effect on enzyme responses to positive allosteric effectors, such as ADP or leucine. Based on the three-dimensional structure of GDH, the mutations may function by impairing the binding of an inhibitory GTP to a domain responsible for the allosteric and cooperativity properties of GDH.

Type I bone morphogenetic protein receptors are expressed on cerebellar granular neurons and a constitutively active form of the type IA receptor induces cerebellar abnormalities.

Cerebellar granular neurons are the most abundant neuronal type in the CNS. Their number and experimental accessibility have made these neurons a valuable model for investigating mechanisms of cell proliferation and differentiation in the CNS. Proliferation of granular neurons is regulated, at least in part, by the secreted protein Sonic Hedgehog, whereas induction and differentiation both appear to be controlled by bone morphogenetic protein (BMP) signaling. Given the role of BMPs in granular cell differentiation, we postulated that BMP receptors (BMPRs) would be expressed on cerebellar granular neurons and that signaling through these receptors is required for normal differentiation. We found that both BMPRIA and BMPRIB are expressed on granular neuron precursors and on mature granular neurons in the developing cerebellum. To determine if these receptors are sufficient for granular cell induction and/or differentiation in vivo, we introduced a constitutively active BMPRIA construct into the developing cerebellum. The resulting cerebelli showed a simplified folial pattern and ectopic collections of small cells located deep in the cerebellar white matter. Phenotypic analysis demonstrated that the ectopic cells are granular neurons. From these data we suggest that signaling through the type I BMPRs occurs during normal cerebellar development and ectopic activation of this pathway affects normal granular neuron development. Furthermore, the similarity of the cerebellar anomalies arising from perturbed BMPR signaling to human cerebellar malformations suggests that dysregulation of BMP signaling may play a pathogenic role in some human cerebellar abnormalities.

Immunodeficiency as a component of recognizable syndromes.

Immunodeficiency occurs in numerous genetic syndromes. While it is the dominant manifestation in primary immunodeficiencies, immune deficits may also be seen in a variety of other recognizable syndromes. Immunodeficiency has been reported in 64 such conditions, adding to the 45 recognized primary immunodeficiencies. These uncommon syndromes with immune defects can present with: (a) growth deficiency (11 syndromes with disproportionate or proportionate short stature), (b) specific organ system dysfunction (18 with gastrointestinal, dermatologic, or neurologic abnormalities), (c) inborn errors of metabolism (13), (d) miscellaneous anomalies (10), or (e) chromosome anomalies (12). In most of the disorders, only some of the affected patients have immune defects. However, in 27 syndromes, immunodeficiency is a constant finding. We briefly review the clinical manifestations of each syndrome and delineate the specific associated immune defects. In most syndromes, the connection between the immune and other defects is unknown. Recognition of these conditions involving both the immune and other organ systems may facilitate accurate diagnosis and management as well as yield information regarding genes critical for the development of the involved systems.

Dominant paternal transmission of Cornelia de Lange syndrome: a new case and review of 25 previously reported familial recurrences.

The Cornelia de Lange syndrome (CdLS) is an autosomal dominant multisystem disorder characterized by somatic and cognitive retardation, characteristic facial features, limb abnormalities, hearing loss, and other organ system involvement. The vast majority of cases (99%) are sporadic, with rare familial occurrences having been reported. Most individuals with CdLS do not reproduce as a result of the severity of the disorder. Maternal transmission has been well documented, as have several cases of multiple-affected children being born to apparently unaffected parents. Paternal transmission has rarely been reported. A case is reported here of a father with classic features of CdLS with a similarly affected daughter. A review of the reported familial cases of CdLS is summarized.

Heterotaxia in a fetus with campomelia, cervical lymphocele, polysplenia, and multicystic dysplastic kidneys: expanding the phenotype of Cumming syndrome.

We report on a fetus with tetramelic campomelia, polysplenia, multicystic dysplastic kidneys, and cervical lymphocele. This condition is similar to the autosomal recessive condition described by Cumming et al. [1986: Am J Med Genet 25:783-790] and is different from campomelic syndrome. In addition, our case had anomalies not previously described in this condition, including abnormal lung lobation with bilateral left bronchial morphology, dextrocardia, total anomalous pulmonary venous return, a left superior vena cava, and a right aortic arch. The pancreas was short, with absence of the body and tail. These anomalies are similar to those found in the polyasplenia spectrum. We suggest that the syndrome reported by Cumming et al. may be expanded to include polysplenia with heterotaxia and that Cumming syndrome may be considered another autosomal recessive condition associated with a laterality defect.

SHH mutation is associated with solitary median maxillary central incisor: a study of 13 patients and review of the literature.

Solitary median maxillary central incisor (SMMCI) or single central incisor is a rare dental anomaly. It has been reported in holoprosencephaly (HPE) cases with severe facial anomalies or as a microform in autosomal dominant HPE (ADHPE). In our review of the literature, we note that SMMCI may also occur as an isolated finding or in association with other systemic abnormalities. These anomalies include short stature, pituitary insufficiency, microcephaly, choanal atresia, midnasal stenosis, and congenital nasal pyriform aperture stenosis. SMMCI can also be a feature of recognized syndromes or associations or a finding in patients with specific chromosomal abnormalities. We performed a molecular study on a cohort of 13 SMMCI patients who did not have HPE. We studied two genes, Sonic Hedgehog (SHH) and SIX3, in which mutations have been reported in patients showing SMMCI as part of the HPE spectrum. A new missense mutation in SHH (I111F), segregating in one SMMCI family, was identified. Our results suggest that this mutation may be specific for the SMMCI phenotype since it has not been found in the HPE population or in normal controls. Published 2001 Wiley-Liss, Inc.

Submicroscopic deletion in cousins with Prader-Willi syndrome causes a grandmatrilineal inheritance pattern: effects of imprinting.

The Prader-Willi syndrome (PWS) critical region on 15q11-q13 is subject to imprinting. PWS becomes apparent when genes on the paternally inherited chromosome are not expressed. Familial PWS is rare. We report on a family in which a male and a female paternal first cousin both have PWS with cytogenetically normal karyotypes. Fluorescence in situ hybridization (FISH) analysis shows a submicroscopic deletion of SNRPN, but not the closely associated loci D15S10, D15S11, D15S63, and GABRB3. The cousins' fathers and two paternal aunts have the same deletion and are clinically normal. The grandmother of the cousins is deceased and not available for study, and their grandfather is not deleted for SNRPN. DNA methylation analysis of D15S63 is consistent with an abnormality of the imprinting center associated with PWS. "Grandmatrilineal" inheritance occurs when a woman with deletion of an imprinted, paternally expressed gene is at risk of having affected grandchildren through her sons. In this case, PWS does not become evident as long as the deletion is passed through the matrilineal line. This represents a unique inheritance pattern due to imprinting.

Skeletal anomalies and deformities in patients with deletions of 22q11.

Skeletal anomalies in patients with a 22q11.2 deletion are reported infrequently. We report the skeletal findings in 108 patients with a 22q11.2 deletion, of whom 37 (36%) had a skeletal anomaly. Twenty-two patients (20%) had anomalies of the limbs, 7 of the upper limb, including preaxial or postaxial polydactyly. An anomaly of the lower limb was found in 16 patients, including postaxial polydactyly, clubfoot, severely overfolded toes, and 2-3 toe cutaneous syndactyly. Chest films of 63 patients were examined; 30% of them had abnormal findings, most commonly supernumerary ribs (17%) or a "butterfly" vertebral body (11%). Hypoplastic vertebrae, hemivertebrae, and vertebral coronal clefts were also noted. Thus, skeletal anomalies are not uncommon in patients with a 22q11.2 deletion and may occur more frequently than recognized previously.

The 22q11.2 deletion: screening, diagnostic workup, and outcome of results; report on 181 patients.

A submicroscopic deletion of chromosome 22q11.2 has been identified in the majority of patients with the DiGeorge syndrome, velocardiofacial syndrome, conotruncal anomaly face syndrome, and in some patients with isolated conotruncal cardiac anomalies, Opitz G/BBB syndrome, and Cayler cardiofacial syndrome. We have evaluated 181 patients with this deletion. We describe our cohort of patients, how they presented, and what has been learned by having the same subspecialists evaluate all of the children. The results help define the extremely variable phenotype associated with this submicroscopic deletion and will assist clinicians in formulating a management plan based on these findings.

The Philadelphia story: the 22q11.2 deletion: report on 250 patients.

A submicroscopic deletion of chromosome 22q11.2 has been identified in the majority of patients with the DiGeorge, velocardiofacial, and conotruncal anomaly face syndromes, and in some patients with the Opitz G/BBB and Cayler cardiofacial syndromes. We have been involved in the analysis of DiGeorge syndrome and related diagnoses since 1982 and have evaluated a large number of patients with the deletion. We describe our cohort of 250 patients whose clinical findings help to define the extremely variable phenotype associated with the 22q11.2 deletion and may assist clinicians in providing genetic counseling and guidelines for clinical management based on these findings.

Hemifacial microsomia in a newborn with hypoplastic skin lesions, an eyelid skin tag, and microphthalmia: an unusual presentation of Delleman syndrome.

Delleman syndrome (oculocerebrocutaneous syndrome) is characterized by orbital cysts, periorbital skin appendages, and focal cutaneous hypoplasia. We describe a male infant with findings associated with this condition, including an eyelid appendage, discrete hypoplastic skin lesions, unilateral microphthalmia, and hydrocephalus. In addition, he had striking unilateral mandibular hypoplasia and microtia, features often present in the oculoauriculovertebral (OAV) spectrum. However, hypoplastic skin lesions and eyelid appendages are not features of the OAV spectrum. The marked degree of hemifacial microsomia present in this child has not been previously noted in Delleman syndrome. Two patients with Delleman syndrome have been previously described who have features typically present in the OAV spectrum. This case demonstrates that characteristics of both Delleman syndrome and the OAV spectrum may be present in one individual.

Syndromes associated with immunodeficiency.

Immunodeficiency often has a genetic basis. Immune defects are the predominant manifestation in primary immunodeficiency disorders, and immune defects may also be associated with a number of other recognizable syndromes. There are 45 recognized primary immunodeficiency disorders, but immunodeficiency has been reported in 105 other syndromes. Abnormalities associated with these syndromes include growth deficiency (19 syndromes with disproportionate or proportionate short stature); specific organ system dysfunction (39 with gastrointestinal, dermatologic, or neurologic abnormalities); inborn errors of metabolism (17); miscellaneous anomalies (17); and chromosome anomalies (13). In most of these disorders, immunodeficiency is present in only a portion of the patients. However, in 49 syndromes, immunodeficiency is present in the vast majority. We review the clinical manifestations of each syndrome and delineate the associated immune defects. For most, the underlying mechanism linking the immune defect and other anomalies is unclear. Recognition of these conditions involving both the immune and other organ systems may facilitate accurate diagnosis and management, as well as yield information regarding genes critical for the development of the involved systems.

Distinctive features in the production of IL-6 by human T cells.

The production of IL-6 was studied in purified populations of human peripheral blood T cells and monocytes. IL-6 could be elicited from both T cells and thymocytes by a variety of polyclonal stimuli. The expression and production of IL-6 in T cells varied in several ways from that of monocytes: (1) under maximal stimulation, T cells secreted 10-fold less IL-6 than did monocytes; (2) by Western blot, the molecular isoforms produced by T cells were distinct from those produced by monocytes, with at least some isoforms being unique to each cell type; (3) the kinetics of IL-6 expression and production was much slower in T cells than in monocytes; (4) the frequency of labeled cells detected by in situ hybridization was 4% for T cells and 34% for monocytes. Our data indicate that there is considerable diversification among cell types in terms of regulation of IL-6 production and possibly in post-translational modifications. This raises the possibility that the IL-6 produced by different cell types may have varying effects depending on the form produced and the timing of synthesis.

Holoprosencephaly: from Homer to Hedgehog.

Holoprosencephaly (HPE), a common developmental defect affecting the forebrain and face, is etiologically heterogeneous and exhibits wide phenotypic variation. Graded degrees of severity of the brain malformation are also reflected in the highly variable craniofacial malformations associated with HPE. In addition, individuals with microforms of HPE, who usually have normal cognition and normal brain imaging, are at risk for having children with HPE. Some obligate carriers for HPE may not have any phenotypic abnormalities. Recurrent chromosomal rearrangements in individuals with HPE suggest loci containing genes important for brain development, and abnormalities in these genes may result in HPE. Recently, Sonic Hedgehog (SHH) was the first gene identified as causing HPE in humans. Proper function of SHH depends on cholesterol modification. Other candidate genes that may be involved in HPE include components of the SHH pathway, elements involved in cholesterol metabolism, and genes expressed in the developing forebrain.

IL-6 enhances the generation of cytolytic T lymphocytes in the allogeneic mixed leucocyte reaction.

Cytolytic T lymphocytes (CTL) require soluble proteins termed lymphokines to develop lytic activity. In this report we have studied two of the lymphokines involved in the development of CTL during the allogeneic mixed leucocyte reaction (MLR). High doses of dendritic cells induced lytic activity from purified CD8+ cells in both the murine and human MLR. Under these conditions, IL-2 and IL-6 were endogenously produced and secreted. Antibodies to IL-2 or the IL-2 receptor blocked CTL formation; however, anti-IL-6 receptor antibodies only partially inhibited the response while anti-IL-6 antibodies were largely ineffective. When limiting numbers of antigen-presenting cells were used CTL failed to develop, and neither IL-2 nor IL-6 was secreted into the culture supernatant. Although the addition of IL-6 to such cultures was ineffective in generating CTL, the combination of IL-2 and IL-6 resulted in a 4-5-fold increase in lytic activity over that of IL-2 alone. We conclude that in the allogeneic MLR, IL-2 and IL-6 contribute to the generation of lytically active CD8+ cells, and the effect of IL-6 is evident when the dose of antigen-presenting cell is limited.

Human developmental disorders and the Sonic hedgehog pathway.

Sonic hedgehog (Shh) is a morphogen that is crucial for normal development of a variety of organ systems, including the brain and spinal cord, the eye, craniofacial structures, and the limbs. Mutations in the human SHH gene and genes that encode its downstream intracellular signaling pathway cause several clinical disorders. These include holoprosencephaly (HPE, the most common anomaly of the developing forebrain), nevoid basal cell carcinoma syndrome, sporadic tumors, including basal cell carcinomas, and three distinct congenital disorders: Greig syndrome Pallister-Hall syndrome, and isolated postaxial polydactyly. These conditions caused by abnormalities in the SHH pathway demonstrate the crucial role of SHH in complex developmental processes, and molecular analyses of these disorders provide insight into the normal function of the SHH pathway in human development.

Interleukin 6 is the principal cytolytic T lymphocyte differentiation factor for thymocytes in human leukocyte conditioned medium.

The formation of CD8+ killer cells from nonlytic thymocyte precursors is mediated by interleukin 2 and a cytokine termed CTL differentiation factor (CDF). While several reports have focused on the effects of recombinant molecules on the development of CTL, the natural protein responsible for CTL development that is produced by normal leukocytes has not been conclusively identified. A 24 kD native protein with CDF activity was enriched from leukocyte conditioned medium and neutralizing antibodies were produced. Utilizing immunoaffinity chromatography and reverse phase chromatography, we purified this CDF to homogeneity. All 21 amino acid residues at the NH2-terminus of CDF were found to be identical to that of IL-6. Natural CDF and IL-6 share many of the same biological properties, including costimulation of thymocyte proliferation with IL-1. Antibodies against CDF or IL-6 can block the activity of either cytokine, and anti-CDF blocks the activity of bulk leukocyte conditioned medium. These results indicate that IL-6 is the principal CTL differentiation factor produced by stimulated human leukocytes.

Identification of novel mutations in SHH and ZIC2 in a South American (ECLAMC) population with holoprosencephaly.

Holoprosencephaly (HPE) is genetically heterogeneous with four genes, SIX3, SHH, TGIF, and ZIC2 that have been identified to date and that are altered in 12% of patients. To analyze this prevalence in a South American population-based sample (57 HPE cases in 244,511 live and still births or 1 in 4300), we performed a mutational study of these genes in 30 unrelated children (26 newborns and 4 non-newborns) with HPE being ascertained by ECLAMC (Latin American Collaborative Study of Congenital Malformations). We identified three novel mutations: two were missense mutations of the SHH gene (Cys183-->Phe; His140-->Pro); the third mutation was a 2-bp deletion in the zinc-finger region of the ZIC2 gene. These molecular results explained 8% (2/26 newborn samples) of the HPE cases in this South American population-based sample, a proportion similar to our previously published data from a collection of cases.