Creation of an international registry to support discovery in schwannomatosis

Schwannomatosis is a tumor suppressor syndrome that causes multiple tumors along peripheral nerves. Formal diagnostic criteria were first published in 2005. Variability in clinical presentation and a relative lack of awareness of the syndrome have contributed to difficulty recognizing affected individuals and accurately describing the natural history of the disorder. Many critical questions such as the mutations underlying schwannomatosis, genotype-phenotype correlations, inheritance patterns, pathologic diagnosis of schwannomatosis-associated schwannomas, tumor burden in schwannomatosis, the incidence of malignancy, and the effectiveness of current, or new treatments remain unanswered. A well-curated registry of schwannomatosis patients is needed to facilitate research in field. An international consortium of clinicians and scientists across multiple disciplines with expertise in schwannomatosis was established and charged with the task of designing and populating a schwannomatosis patient registry. The International Schwannomatosis Registry (ISR) was built around key data points that allow confirmation of the diagnosis and identification of potential research subjects to advance research to further the knowledge base for schwannomatosis. A registry with 389 participants enrolled to date has been established. Twenty-three additional subjects are pending review. A formal process has been established for scientific investigators to propose research projects, identify eligible subjects, and seek collaborators from ISR sites. Research collaborations have been created using the information collected by the registry and are currently being conducted. The ISR is a platform from which multiple research endeavors can be launched, facilitating connections between affected individuals interested in participating in research and researchers actively investigating a variety of aspects of schwannomatosis. © 2016 Wiley Periodicals, Inc.

Phenotype characterization and natural history of spondylothoracic dysplasia syndrome: a series of 27 new cases

Spondylothoracic dysplasia (STD, MIM#277300) is an autosomal recessive disorder with high prevalence in the Puerto Rican population. It is generally regarded as a lethal condition. Since Jarcho and Levin described it in 1938, it has been referred to as spondylocostal dysplasia, costovertebral dysplasia, Jarcho-Levin syndrome and STD. We have prospectively characterized 27 patients with STD by detailed physical examination, pedigree analysis, thoracic CT scans, and pulmonary function tests (PFTs). Diagnoses were established using spinal radiographs and 3-D reconstructive CT scans to demonstrate fusion of the ribs at the costo-vertebral junction with a fan-like (crab-like) configuration of the thorax. Vertebral segmentation and formation defects were seen throughout the spine with a decrease in the number of vertebral bodies. Characteristic vertebral shape consisted of a decrease in antero-posterior diameter and an increase in lateral length, giving the vertebra a sickle shape. Eight out of 18 prospectively follow patients died within the first 6 months of life, a 44% mortality rate. Cause of death was respiratory insufficiency secondary to pneumonia and pulmonary restriction. This is an important finding since the vast majority of STD syndrome patients cited in the medical literature have died in the newborn and early childhood periods. Age of the remaining patients ranged from 4 months to 47 years. This represents the largest collection of patients with STD reported and it has allowed us to determine a detailed phenotype. Given 56% survival at 6 months, we show that STD is not a lethal syndrome.

Malignant peripheral nerve sheath tumours in neurofibromatosis type 1: MRI supports the diagnosis of malignant plexiform neurofibroma

Plexiform neurofibroma (PNF) is a typical feature of neurofibromatosis 1 (NF1). About 10% of patients with NF1 develop malignant peripheral nerve-sheath tumours (MPNST), usually arising from PNF, and this is the major cause of poor survival. A better prognosis can be achieved if the tumours are diagnosed at an early stage. Our objective was to establish MRI criteria for MPNST and to test their usefulness in detecting early malignant change in PNF. MRI was performed on 50 patients with NF1 and nerve-sheath tumours, of whom seven had atypical pain, tumour growth or neurological deficits indicative of malignancy; the other 43 were asymptomatic. On MRI all seven symptomatic patients had inhomogeneous lesions, due to necrosis and haemorrhage and patchy contrast enhancement. In one patient, the multiplicity of confluent tumours with inhomogeneous areas in addition to central lesions did not allow exclusion of malignancy. Only three of the 43 asymptomatic patients had comparable changes; the other 40 patients had tumours being of relatively homogeneous structure on T1- and T2-weighted images before and after contrast enhancement. All three asymptomatic patients with inhomogeneous lesions were shown to have MPNST.

Growth type of plexiform neurofibromas in NF1 determined on magnetic resonance images

This article describes some types of growth in plexiform neurofibroma (PNF) on magnetic resonance images (MRI). This tumor is almost exclusively associated with NF1. On MRI, the tumor is depicted as a hyperintensive area on T2-weighted images. We distinguished 3 patterns of tumor growth: first, the superficial and non-invasive tumors, that are restricted to the cutis and subcutis, only eventually having outgrowth to the muscles beneath and are slow growing. Second, the displacing PNF that develop in deeper layers of the skin or within the body. They can grow to a large extent but do not invade adjacent muscles or skin. Thirdly, the invasive type with no visible margins that cannot be resected without adjacent structures or organs. A combination of these tumors can sometimes be noted, e.g. a displacing tumorous nerve developing in a large lumpy, non-invasive PNF. These categories might be used as a current guideline for medical advice, surgical treatment planning and medication trials.

Plexiform neurofibromas in NF1: toward biologic-based therapy

Neurofibromatosis type 1 (NF1) is one of the most common neurogenetic diseases affecting adults and children. Neurofibromas are one of the most common of the protean manifestations of NF1. Plexiform neurofibromas, which will frequently cause cosmetic abnormalities, pain, and neurologic deficits, are composed of "neoplastic" Schwann cells accompanied by other participating cellular and noncellular components. There is increasing evidence that loss of NF1 expression in neoplastic Schwann cells is associated with elevated levels of activated RAS, supporting the notion that the NF1 gene product, neurofibromin, acts as a growth regulator by inhibiting ras growth-promoting activity. In addition, there is increasing evidence that other cooperating events, which may be under cytokine modulation, are important for neurofibroma development and growth. Treatment of plexiform neurofibromas has been empiric, with surgery being the primary option for those with progressive lesions causing a major degree of morbidity. The efficacy of alternative treatment approaches, including the use of antihistamines, maturation agents, and antiangiogenic drugs, has been questionable. More recently, biologic-based therapeutic approaches, using drugs that target the molecular genetic underpinnings of plexiform neurofibromas or cytokines believed important in tumor growth, have been initiated. Evaluation of such trials is hindered by the unpredictable natural history of plexiform neurofibromas and difficulties in determining objective response in tumors that are notoriously large and irregular in shape. Innovative neuroimaging techniques and the incorporation of quality-of-life scales may be helpful in evaluation of therapeutic interventions. The ability to design more rational therapies for NF1-associated neurofibromas is heavily predicated on an improved understanding of the molecular and cellular biology of the cells involved in neurofibroma formation and growth.

Abdominal migraine in children with neurofibromatosis type 1: a case series and review of gastrointestinal involvement in NF1

BACKGROUND

Symptomatic involvement of the gastrointestinal tract in children with neurofibromatosis type 1 (NF1) is rare. Most reported complications in adults are caused by the presence of neurofibromas in the stomach, small bowel, or mesentery. In contrast, abdominal pain in children with NF1 may be the result of nonanatomic causes, such as migraine. There are no previous reports of an association between abdominal migraine and NF1.

METHODS

Children with abdominal migraine were identified from a group of children with NF1, all of whom had been followed up for a minimum of 3 years. Medical records of cases were reviewed independently by two authors. MEDLINE was searched via PubMed for all reports of children with NF1 and any associated gastrointestinal involvement.

RESULTS

Six children with NF1 and intermittent, episodic, severe abdominal pain are reported. Investigations for obstructive or inflammatory causes of abdominal pain were negative. All patients had previously been diagnosed with migraine headaches by a neurologist. In five of the six patients, propranolol (10-15 mg three times daily) resulted in relief of their abdominal pain within days of starting therapy. Our review identified 24 children in the medical literature with gastrointestinal complications of NF1, mostly secondary to visceral neurofibromas. In almost all of these cases, clinical examination and simple radiologic investigations led to the definitive diagnosis. There were no reports of abdominal migraine complicating NF1.

CONCLUSIONS

Abdominal pain secondary to migraine is an unrecognized cause of abdominal pain in children with NF1 and may be more common than anatomic causes of abdominal pain in children with NF1. In children with NF1 and severe recurrent abdominal pain in whom an evaluation for anatomic lesions is negative, a trial of migraine therapy may be indicated.

Establishing priorities in neurofibromatosis research: a workshop summary

Progress in understanding the biology of the neurofibromatoses (NF1 and NF2) offers hope for the development of new, effective methods of treatment. In May 2000, the National Institute of Neurological Disorders and Stroke (NINDS) hosted a workshop that included leading researchers and clinicians from the NF community. The goal of the meeting was to assess current knowledge and identify priorities for future research. Needs identified included the development of better animal models, further study of the function of the NF1 and NF2 genes, and investigation of the role of modifier genes. The participants agreed that it will also be important to define further the natural history of NF1 and NF2 and to develop an infrastructure to support clinical trials. They also discussed the possible creation of research consortia and NF centers to promote the integration of basic and clinical research.

Identification of a novel genetic locus for familial cardiac myxomas and Carney complex

BACKGROUND

Intracardiac myxomas are significant causes of cardiovascular morbidity and mortality through embolic stroke and heart failure. In the autosomal dominant syndrome Carney complex, intracardiac myxomas arise in the setting of lentiginosis and other lesions associated with cutaneous hyperpigmentation, extracardiac myxomas, and nonmyxomatous tumors. Genetic factors that regulate cardiac tumor growth remain unknown.

METHODS AND RESULTS

We used the molecular genetic techniques of linkage analysis to study 4 kindreds affected by Carney complex to determine the genetic basis of this syndrome. Our investigation confirmed genetic heterogeneity of Carney complex. Moreover, genetic linkage analysis with polymorphic short tandem repeats on the long arm of chromosome 17 revealed maximal pairwise LOD scores of 5.9, 1.5, 1.8, and 2.9 for families YA, YB, YC01, and YC11, respectively. Haplotype analysis excluded a founder effect at this locus. These data identify a major 17 cM locus on chromosome 17q2 that contains the Carney complex disease gene.

CONCLUSIONS

The ultimate identification and analysis of the Carney complex disease gene at this human chromosome 17q2 locus will facilitate diagnosis and treatment of cardiac myxomas and will foster new concepts in regulation of cardiac cell growth and differentiation.

Genetic variation in the 3' untranslated region of the neurofibromatosis 1 gene: application to unequal allelic expression

Neurofibromatosis type 1 (NF1) is a common genetic disorder caused by inactivation of neurofibromin, a protein capable of modulating signal transduction by activating Ras-GTPase activity. We have used cDNA cloning and Northern blot analysis to confirm the NF1 gene produces alternatively polyadenylated mRNAs with 3' untranslated regions (3' UTR) that show striking evolutionary conservation. Scanning of the 3'UTRs for genetic variation revealed three common sequence polymorphisms (> 30% heterozygosity), one less informative polymorphism (approximately 5% heterozygosity) and one rare variant (1/144 chromosomes). These differences were used to examine relative levels of expression of normal and mutant NF1 alleles in lymphoblast cell lines and in one case, autopsy tissue, from patients with NF1. Unequal allelic expression (up to 4-fold) was observed in a subset of both sporadic and familial NF1 cases. Where linkage phase could be determined, the allele segregating with the disorder displayed a relative reduction in expression. However, the magnitude of this effect was variable suggesting the operation of additional, non-genetic factors in determining the degree of relative expression of the mutant allele.

The diagnostic evaluation and multidisciplinary management of neurofibromatosis 1 and neurofibromatosis 2

OBJECTIVE

Neurofibromatosis 1 and neurofibromatosis 2 are autosomal dominant genetic disorders in which affected individuals develop both benign and malignant tumors at an increased frequency. Since the original National Institutes of Health Consensus Development Conference in 1987, there has been significant progress toward a more complete understanding of the molecular bases for neurofibromatosis 1 and neurofibromatosis 2. Our objective was to determine the diagnostic criteria for neurofibromatosis 1 and neurofibromatosis 2, recommendations for the care of patients and their families at diagnosis and during routine follow-up, and the role of DNA diagnostic testing in the evaluation of these disorders.

DATA SOURCES

Published reports from 1966 through 1996 obtained by MEDLINE search and studies presented at national and international meetings.

STUDY SELECTION

All studies were reviewed and analyzed by consensus from multiple authors.

DATA EXTRACTION

Peer-reviewed published data were critically evaluated by independent extraction by multiple authors.

DATA SYNTHESIS

The main results of the review were qualitative and were reviewed by neurofibromatosis clinical directors worldwide through an Internet Web site.

CONCLUSIONS

On the basis of the information presented in this review, we propose a comprehensive approach to the diagnosis and treatment of individuals with neurofibromatosis 1 and neurofibromatosis 2.

The diagnostic evaluation and multidisciplinary management of neurofibromatosis 1 and neurofibromatosis 2

OBJECTIVE

Neurofibromatosis 1 and neurofibromatosis 2 are autosomal dominant genetic disorders in which affected individuals develop both benign and malignant tumors at an increased frequency. Since the original National Institutes of Health Consensus Development Conference in 1987, there has been significant progress toward a more complete understanding of the molecular bases for neurofibromatosis 1 and neurofibromatosis 2. Our objective was to determine the diagnostic criteria for neurofibromatosis 1 and neurofibromatosis 2, recommendations for the care of patients and their families at diagnosis and during routine follow-up, and the role of DNA diagnostic testing in the evaluation of these disorders.

DATA SOURCES

Published reports from 1966 through 1996 obtained by MEDLINE search and studies presented at national and international meetings.

STUDY SELECTION

All studies were reviewed and analyzed by consensus from multiple authors.

DATA EXTRACTION

Peer-reviewed published data were critically evaluated by independent extraction by multiple authors.

DATA SYNTHESIS

The main results of the review were qualitative and were reviewed by neurofibromatosis clinical directors worldwide through an Internet Web site.

CONCLUSIONS

On the basis of the information presented in this review, we propose a comprehensive approach to the diagnosis and treatment of individuals with neurofibromatosis 1 and neurofibromatosis 2.

Genetic heterogeneity of familial atrial myxoma syndromes (Carney complex)

Familial atrial myxomas may present as a component of the Carney complex, an autosomal dominant multiple neoplasia and lentiginosis syndrome. Although a gene defect for the Carney complex in some families maps to chromosome 2p, this syndrome is genetically heterogeneous, and other genetic loci also produce familial atrial myxomas.

Limb anomalies in DiGeorge and CHARGE syndromes

Limb anomalies are not common in the DiGeorge or CHARGE syndromes. We describe limb anomalies in two children, one with DiGeorge and the other with CHARGE syndrome. Our first patient had a bifid left thumb, Tetralogy of Fallot, absent thymus, right facial palsy, and a reduced number of T-cells. A deletion of 22q11 was detected by fluorescence in situ hybridization (FISH). The second patient, with CHARGE syndrome, had asymmetric findings that included right fifth finger clinodactyly, camptodactyly, tibial hemimelia and dimpling, and severe club-foot. The expanded spectrum of the DiGeorge and CHARGE syndromes includes limb anomalies.

Allele-specific replication of 15q11-q13 loci: a diagnostic test for detection of uniparental disomy

Allele-specific replication differences have been observed in imprinted chromosomal regions. We have exploited this characteristic of an imprinted region by using FISH at D15S9 and SNRPN (small nuclear ribonucleo protein N) on interphase nuclei to distinguish between Angelman and Prader-Willi syndrome patient samples with uniparental disomy of chromosome 15q11-q13 (n = 11) from those with biparental inheritance (n = 13). The familial recurrence risks are low when the child has de novo uniparental disomy and may be as high as 50% when the child has biparental inheritance. The frequency of interphase cells with asynchronous replication was significantly lower in patients with uniparental disomy than in patients with biparental inheritance. Within the sample population of patients with biparental inheritance, those with altered methylation and presumably imprinting center mutations could not be distinguished from those with no currently detectable mutation. This test is cost effective because it is performed on interphase cells from the same hybridized cytological preparation in which a deletion is excluded, and additional specimens are not required to determine the parental origin of chromosome 15.

Preliminary phenotypic map of chromosome 4p16 based on 4p deletions

We have collected and analyzed clinical information from 11 patients with chromosome 4p deletions or rearrangements characterized by various molecular techniques. Comparing the extent of these patients' deletions with their respective clinical presentations led to the proposal of a preliminary phenotypic map of chromosome 4p. This map consists of regions which, when deleted, are associated with specific clinical manifestations. Nonspecific changes such as mental and growth retardation are not localized, and probably result from the deletion of more than one gene or region. The region associated with most of the facial traits considered typical in Wolf-Hirschhorn syndrome (WHS) patients coincides with the currently proposed WHS critical region (WHSCR), but some anomalies commonly seen in WHS appear to map outside of the WHSCR. The observation of clinodactyly in 2 patients with nonoverlapping deletions allows assignment of these defects to at least 2 separate regions in 4p16. These initial observations and attempts at genotype/phenotype correlation lay the groundwork for identifying the genetic basis of these malformations, a common objective of gene mapping efforts and chromosome deletion studies.

The Human Genome Project: implications for the practicing obstetrician

The Human Genome Project is an international effort to discern the complete genetic makeup of human beings. The isolation and characterization of genes will offer tremendous opportunities for disease detection, diagnosis, screening, prevention, and counseling. Advances in genetic research are occurring simultaneously with the development of new techniques for prenatal genetic testing. Use of gene therapy in humans likely will lag behind our ability to detect genetic disorders. Consequently, obstetricians will be forced to face some difficult medical, ethical, and social challenges. The possibility of a national cystic fibrosis screening program is an example of the complex problems we will face as new genes are described. The obstetric community needs to participate actively in the debate surrounding the ethical and legal implications of the Human Genome Project. We need to establish clinical standards and use our professional organization to act as a resource for clinicians, the public, and legislatures. Because of the increased requirement for genetic counseling, we recommend an expansion of genetics training for residents and clinicians and the development of computer-based interactive video programs for genetic counseling.

Interstitial deletion of distal chromosome 4p in a patient without classical Wolf-Hirschhorn syndrome

We report on a patient with a de novo interstitial deletion of chromosome 4p; 46,XY,del(4) (p15.31p16.3). The cytogenetic diagnosis would predict a patient with the Wolf-Hirschhorn syndrome (WHS) since deletions of 4p16 are associated with WHS [Wilson et al., 1981]. This patient lacks the facial characteristics of WHS, but has some anomalies of WHS that are also commonly seen in other syndromes, i.e., severe growth retardation, developmental delay, and hypospadias. His molecular distal breakpoint occurs in 4p16.3 as defined by fluorescence in situ hybridization and Southern blot analysis, and his deletion does not overlap with the currently proposed WHS critical region. This case gives further support to the distal position of the WHS critical region and demonstrates some of the WHS associated phenotypes that can be attributed to a deletion of the proximal third of 4p16.3.

A syndrome of autosomal dominant alternating hemiplegia: Clinical presentation mimicking intractable epilepsy; chromosomal studies; and physiologic investigations

We report the familial occurrence and apparent autosomal dominant inheritance of alternating hemiplegia of childhood. The proband, a 9-year-old boy, presented with developmental retardation, rare tonic-clonic seizures, and frequent episodes of flaccid alternating hemiplegia that had been presumed to represent postictal paralysis. The hemiplegia spells, which started in his first year, did not respond to multiple antiepileptics. Between attacks, there was choreoathetosis and dystonic posturing. Father, brother, paternal uncle, and paternal grandmother had similar histories of alternating hemiplegia. Investigations included negative CT, metabolic, and coagulation studies. EEG and SPECT 99mTc exametazime scanning failed to reveal any significant slowing or any major changes in cortical perfusion during hemiplegia as compared with nonhemiplegic periods. The karyotype revealed a balanced reciprocal translocation, 46,XY,t(3;9)(p26;q34) in the patient, in all the affected living relatives, and in one apparently unaffected sibling. The asymptomatic mother had a normal karyotype. Analysis of DNA markers was consistent with the karyotype results. Both affected siblings were treated with and responded to flunarizine therapy, with a greater than 70% decrease in attack frequency. Documented flunarizine trough serum concentrations were 28.9 ng/ml in the proband and 6.6 ng/ml in his brother.

Prediction of dystrophin phenotype by DNA analysis in Duchenne/Becker muscular dystrophy

Allele-specific molecular diagnosis of Duchenne and Becker muscular dystrophies (DMD and BMD) has been largely dependent upon muscle biopsy for dystrophin protein assay. We performed lymphocyte DNA mutation analysis by polymerase chain reaction on 14 boys presenting with a clinical picture compatible with DMD or BMD. DNA analysis revealed that 12 of 14 boys had a deletion of the dystrophin gene, thus establishing the diagnosis of DMD/BMD. Furthermore, genotypes for 9 of 12 deletion patients permitted prediction of the specific allelic disorder (i.e., DMD or BMD). Subsequent dystrophin testing confirmed all of the DNA-based diagnoses. We propose that DNA mutation analysis be included in the initial evaluation of patients suspected of having DMD/BMD, thus potentially eliminating the need for muscle biopsy in the majority of patients.

Immunocytochemical demonstration of interphotoreceptor retinoid-binding protein in cerebellar medulloblastoma

Previously, immunoreactive rod-opsin and S-antigen (arrestin), two highly characteristic markers of retinal photoreceptors and pinealocytes, were shown to be present in certain medulloblastoma cells. It, thus, has been suggested that such cells differentiate along the photoreceptor lineage. This is corroborated in the present immunocytochemical investigation using antibodies against another photoreceptor-cell marker, the interphotoreceptor retinoid-binding protein (IRBP). As shown in preparations of human retina and pineal organ, IRBP can be successfully demonstrated in formalin-fixed and paraffin-embedded tissue: the IRBP immunoreaction is located to the outer and inner segments of retinal photoreceptor cells and to perikarya of certain pinealocytes. Examination of formalin-fixed, paraffin-embedded biopsy specimens of 66 cerebellar medullo-blastomas revealed varying numbers of IRBP-immuno-reactive tumor cells in 19 cases that were formerly shown to contain rod-opsin and S-antigen immunoreaction. IRBP-immunoreactive tumor cells were also found in a retinoblastoma and a pineocytoma, but not in neuroblastoma, ganglioneuroblastoma, glioblastoma, oligodendroglioma and astrocytoma. The results indicate: (1) cerebellar medulloblastomas are heterogeneous in their differentiation potential; (2) one type of medulloblastoma displays photoreceptor characteristics; (3) this type appears to be closely related to retinoblastoma and pineal cell tumors; and (4) all three types of tumors may display additional common features to be explored in future studies.

Stage IV neuroblastoma in infants. Long-term survival

Before the advent of multiagent chemotherapy, the prognosis for patients with Stage IV neuroblastoma of all ages was dismal. More recently, marked improvement in infants with Stage IV neuroblastoma has been reported. Twenty-four infants with Stage IV neuroblastoma have been treated at the Dana-Farber Cancer Institute/The Children's Hospital, and the Joint Center For Radiation Therapy, Boston, Massachusetts, between 1970 and 1988. Twenty-three of these patients were treated with multiagent chemotherapy and one with a single drug. In the initial report, ten of 11 patients were alive without evidence of disease after intensive therapy. In this report the authors update their initial series of patients and include 13 additional patients who subsequently presented to our institutions with Stage IV neuroblastoma younger than 1 year of age. The 5-year actuarial event-free survival for the 24 patients is 75%. No patient without bone metastases died from neuroblastoma, and 12 of 16 patients with bone metastases remained disease free. These results confirm that infants with Stage IV neuroblastoma have a very good prognosis when treated with intensive multiagent chemotherapy.

Consistent cytogenetic aberrations in hepatoblastoma: a common pathway of genetic alterations in embryonal liver and skeletal muscle malignancies?

Cytogenetic analyses of four consecutive hepatoblastomas revealed near-diploid stemline karyotypes with relatively simple chromosome aberrations. Cytogenetic abnormalities shared by each tumor included trisomy for all of part of chromosome 2 and trisomy for chromosome 20. In two cases, partial trisomy for chromosome 2 resulted from direct duplication of long arm material with the shortest region of overlap being 2q23-2q35. In one tumor, each metaphase also contained a variable number of double minute chromosomes found not to derive from NMYC amplification. Interestingly, trisomy for 2q and trisomy 20 are also characteristic events in pediatric embryonal rhabdomyosarcomas. Furthermore, others have reported loss of heterozygosity for the short arm of chromosome 11 in both hepatoblastoma and childhood embryonal rhabdomyosarcoma, and both these malignant diseases are associated with Beckwith-Wiedemann syndrome. These cytogenetic and molecular findings suggest a parallel pathway of genetic steps in the initiation and/or progression of tumors of embryonal liver and skeletal muscle.

Phenotypic heterogeneity of spinal muscular atrophy mapping to chromosome 5q11.2-13.3 (SMA 5q)

We made phenotypic analysis of 14 families with spinal muscular atrophy (SMA) linking to chromosome 5q11.2-13.3 (SMA 5q), and 2 that may not map to this locus, to assess clinical symptoms among SMA families known to result from mutation at the identical gene/locus. Although the current number of families is still small, the correlation of clinical phenotype and molecular genotype supports 2 observations. First, SMA mutations at the 5q locus present with a broad continuum of clinical abnormalities, and 2nd, the single clearly unlinked family presents with an unusual phenotype characterized by relatively late onset and early death. Thus, there are as yet no unambiguous cases of typical SMA families that are clearly unlinked to the locus at 5q-ie, no clear cases of nonallelic heterogeneity. Analysis of SMA 5q families supports the view that, with certain exceptions, there is little phenotypic intrafamilial variability. When families were ranked by severity of disease there was a strong correlation with age of onset. Onset within the 1st few months was associated with early death, but not in all cases. With rare exception, onset after 1 year of age was associated with less severe disease and greater longevity.

Ontogenetic development of S-antigen- and rod-opsin immunoreactions in retinal and pineal photoreceptors of Xenopus laevis in relation to the onset of melatonin-dependent color-change mechanisms

In Xenopus laevis Daud., the ontogenetic occurrence of two photoreceptor-specific proteins, S-antigen and rod-opsin, was investigated and correlated to the maturation of the neurohormonal effector system involved in melatonin-dependent color-change mechanisms. Tadpoles ranging from stage 12 to 57 (Nieuwkoop and Faber 1956) were fixed in Zamboni's or Bouin's solution. Frozen or paraffin sections of either total heads or dissected brains and eyes were prepared and treated with highly specific antisera against S-antigen and rod-opsin. In the retina, immunoreactive S-antigen and rod-opsin were first demonstrated in a few centrally located photoreceptors at stage 37/38. Photoreceptors of the peripheral (iridical) portions of the retina gradually became immunoreactive during further development. As in the retina, the first S-antigen-immunoreactive photoreceptors in the pineal complex appeared at stage 37/38. At this and all later stages investigated rod-opsin immunoreactivity was restricted to a few dot-like structures resembling developing pineal outer and inner segments. In most animals rod-opsin immunoreactivity was completely absent from the pineal complex. The analysis of retinal proteins with the immunoblotting technique (Western blot) revealed that the S-antigen antibody bound to a 48-kDa protein and the rod-opsin antibody to a 38-kDa protein. The body lightening reaction was determined with the aid of the melanophore index in larvae fixed in light or darkness, respectively. Aggregation of melanophore melanosomes in darkness (the melatonin-dependent primary chromatic response) first occurred at stage 37/38 when melanophores started to differentiate and became pigmented. These results indicate that in Xenopus laevis (i) the molecular mechanisms of photoreception develop simultaneously in retina and pineal complex; (ii) most pineal photoreceptors differ from retinal rods in that they contain immunoreactive S-antigen but essentially no immunoreactive rod-opsin; and (iii) the differentiation of phototransduction processes coincides with the onset of melatonin-dependent photoneuroendocrine regulation of color-change mechanisms.

Rapid cloning of multiple amplified nucleotide sequences from human neuroblastoma cell lines by phenol emulsion competitive DNA reassociation

A protocol for the rapid cloning of many DNA fragments from an amplified genomic region is described. The procedure is based on a modification of the phenol-emulsion reassociation technique (PERT) previously used to clone DNA fragments missing from a chromosomal deletion [Kunkel et al., Proc. Natl. Acad. Sci. USA 82 (1985) 4778-4782]. The procedure was used to construct recombinant libraries in the plasmid pBR322 which were highly enriched for amplified sequences from two neuroblastoma cell lines, CHP-126 and IMR-32. Many new amplified DNA fragments were isolated from these libraries, indicating that the PERT methodology should be of general use in isolating amplified DNA from other cell lines and tumors.

Amplification and rearrangement of DNA sequences from the chromosomal region 2p24 in human neuroblastomas

Seven DNA fragments which map to or very near human chromosome band 2p24 are shown to be differentially amplified in DNA from specific subsets of an enlarged series of human neuroblastoma cell lines and primary neuroblastomas. Of these DNA fragments, the probe NB-19-21 for the oncogene N-myc is the most frequently amplified, with a second expressed sequence (pG21) amplified in 9 of those 11 cell lines and 16 of those 25 tumors exhibiting amplification of N-myc. The remaining probes are in turn each amplified in progressively smaller, nested subsets of the cell lines and tumors in which both N-myc and pG21 are amplified. These data permit construction of models for the organization of a "neuroblastoma amplicon," i.e., an originally amplified DNA domain, with N-myc positioned most central and the other DNA fragments increasingly peripheral; comparable models result for the cell lines and the tumors. Five of the seven probes examined detect novel DNA fragments in these specimens, reinforcing previous observations that extensive DNA rearrangement can occur during DNA amplification in neuroblastoma cell lines and in primary neuroblastomas. Such rearrangements could contribute significantly to the evolution of the neuroblastoma amplicon in different specimens to progressively smaller units, preserving, in the limit, amplification of N-myc.

Bilateral lucency of the globus pallidus complicating methylmalonic acidemia

A child was seen because of encephalopathy and metabolic ketoacidosis at 19 months. She was found to have a cobalamin-responsive form of methylmalonic acidemia of the cbl A complementation group. However, after treatment with cyanocobalamin and a protein-restricted diet, with recovery from the encephalopathy, she was found to have a tremor and bilateral dystonic posturing in association with lucencies in the globus pallidi shown by computed tomographic scan.

Differential amplification, assembly, and relocation of multiple DNA sequences in human neuroblastomas and neuroblastoma cell lines

DNA amplification, manifested by homogeneously staining regions in chromosomes and by extrachromosomal, double minute bodies, is characteristic of many neuroblastoma cell lines. Sequences recruited from a specific domain on the short arm of chromosome 2 (2p) are amplified in advanced-stage primary neuroblastomas, whereas sequences from distinctly different regions of 2p are amplified in the neuroblastoma cell line IMR-32. Five different DNA segments, which include the oncogene N-myc, three other fragments derived from the homogeneously staining region of the neuroblastoma cell line IMR-32, and a fifth fragment, derived from the neuroblastoma cell line NB-9, showed differential and variable amplification in 24 advanced-stage neuroblastoma tumors out of 112 tested specimens. All five fragments were mapped within the chromosomal region 2p23-2p25 by three different approaches. However, eight other fragments cloned from the homogeneously staining region of IMR-32 cells, which were not amplified in the tumor tissues examined, were mapped to two more proximal domains of 2p, thousands of kilobases apart from each other and from the chromosomal domain that is amplified in the tumors. These results establish the amplification, to different degrees, of a variable-sized segment of one domain near the terminus of 2p in advanced neuroblastomas. These tumors might ultimately be distinguished according to the pattern of amplification of DNA segments within this domain. The data presented also indicate the existence of a new and complex amplification mechanism in at least one neuroblastoma cell line (IMR-32), which involves not only relocation of DNA from specific genomic domains but also the formation of novel units by splicing together very distant DNA segments.