Dolichol phosphate mannose synthase (DPM1) mutations define congenital disorder of glycosylation Ie (CDG-Ie)

Congenital disorders of glycosylation (CDGs) are metabolic deficiencies in glycoprotein biosynthesis that usually cause severe mental and psychomotor retardation. Different forms of CDGs can be recognized by altered isoelectric focusing (IEF) patterns of serum transferrin (Tf). Two patients with these symptoms and similar abnormal Tf IEF patterns were analyzed by metabolic labeling of fibroblasts with ¿2-(3)Hmannose. The patients produced a truncated dolichol-linked precursor oligosaccharide with 5 mannose residues, instead of the normal precursor with 9 mannose residues. Addition of 250 microM mannose to the culture medium corrected the size of the truncated oligosaccharide. Microsomes from fibroblasts of these patients were approximately 95% deficient in dolichol-phosphate-mannose (Dol-P-Man) synthase activity, with an apparent K(m) for GDP-Man approximately 6-fold higher than normal. DPM1, the gene coding for the catalytic subunit of Dol-P-Man synthase, was altered in both patients. One patient had a point mutation, C(274)G, causing an R(92)G change in the coding sequence. The other patient also had the C(274)G mutation and a 13-bp deletion that presumably resulted in an unstable transcript. Defects in DPM1 define a new glycosylation disorder, CDG-Ie.

Array comparative genomic hybridisation analysis of boys with X linked hypopituitarism identifies a 3.9 Mb duplicated critical region at Xq27 containing SOX3.

INTRODUCTION: Array comparative genomic hybridisation (array CGH) is a powerful method that detects alteration of gene copy number with greater resolution and efficiency than traditional methods. However, its ability to detect disease causing duplications in constitutional genomic DNA has not been shown. We developed an array CGH assay for X linked hypopituitarism, which is associated with duplication of Xq26-q27. METHODS: We generated custom BAC/PAC arrays that spanned the 7.3 Mb critical region at Xq26.1-q27.3, and used them to search for duplications in three previously uncharacterised families with X linked hypopituitarism. RESULTS: Validation experiments clearly identified Xq26-q27 duplications that we had previously mapped by fluorescence in situ hybridisation. Array CGH analysis of novel XH families identified three different Xq26-q27 duplications, which together refine the critical region to a 3.9 Mb interval at Xq27.2-q27.3. Expression analysis of six orthologous mouse genes from this region revealed that the transcription factor Sox3 is expressed at 11.5 and 12.5 days after conception in the infundibulum of the developing pituitary and the presumptive hypothalamus. DISCUSSION: Array CGH is a robust and sensitive method for identifying X chromosome duplications. The existence of different, overlapping Xq duplications in five kindreds indicates that X linked hypopituitarism is caused by increased gene dosage. Interestingly, all X linked hypopituitarism duplications contain SOX3. As mutation of this gene in human beings and mice results in hypopituitarism, we hypothesise that increased dosage of Sox3 causes perturbation of pituitary and hypothalamic development and may be the causative mechanism for X linked hypopituitarism.

Familial splenomegaly: macrophage hypercatabolism of lipoproteins associated with apolipoprotein E mutation [apolipoprotein E (delta149 Leu)].

Splenomegaly with sea-blue histiocytes is not associated with dyslipidemia, except in severe cases of hypertriglyceridemia, Tangier disease, or lecithin cholesterol acyltransferase deficiency. We describe two kindreds in which the sea-blue histiocyte syndrome was associated with an apoE variant in the absence of severe dyslipidemia. Both patients presented with mild hypertriglyceridemia and splenomegaly. After splenectomy both patients developed severe hypertriglyceridemia. Pathological evaluation of the spleen revealed the presence of sea-blue histiocytes. A mutation of apoE was demonstrated, with a 3-bp deletion resulting in the loss of a leucine at position 149 in the receptor-binding region of the apoE molecule [apoE (delta149 Leu)]. Although both probands were unrelated, they were of French Canadian ancestry, suggesting the possibility of a founder effect. In summary, we describe two unrelated probands with primary sea-blue histiocytosis who had normal or mildly elevated serum triglyceride concentrations that markedly increased after splenectomy. In addition, we provide evidence linking the syndrome to an inherited dominant mutation in the apoE gene, a 3-bp deletion on the background of an apoE 3 allele that causes a derangement in lipid metabolism and leads to splenomegaly in the absence of severe hypertriglyceridemia.

Familial occurrence of carcinoid tumors and association with other malignant neoplasms.

Carcinoid tumors are generally thought to be sporadic, except for a small proportion that occur as a part of multiple endocrine neoplasia syndromes. Data regarding the familial occurrence of carcinoid as well as its potential association with other neoplasms are limited. A chart review was conducted on patients indexed for malignant carcinoid tumor of the gastrointestinal tract seen at the Mayo Clinic between 1988 and 1996. A survey of family history of malignancies and personal history of other tumors was mailed to all eligible patients. Data for 245 patients were analyzed. Observed rates of carcinoids and other malignancies were compared with Surveillance, Epidemiology, and End Results data. Estimates of the cumulative probability for first-degree relatives developing a carcinoid tumor were calculated. Nine (3.7%) patients with carcinoid tumor had at least one first-degree relative with the same malignancy. The rate of carcinoid tumor in first-degree relatives of probands was higher (P < 0.0001) than expected based on the Surveillance, Epidemiology, and End Results population data. Cumulative probability in a first-degree relative for developing a carcinoid was calculated to be 1.5% at age 80. There was an increased risk for developing a carcinoid tumor among first-degree relatives of patients with carcinoid. Neither patients with carcinoid nor their first-degree relatives had an increased incidence of other malignancies.

Ordering and interpreting DNA tests.

DNA testing has become relatively common during the past few years. All humans have an estimated five to eight mutated genes and are at risk for a genetic disorder. Recognition of these facts and development of DNA technology have created substantial interest in DNA testing as a diagnostic and management tool. As with any emerging technology, the applications and limitations must be understood in order to use the new tests wisely. In this review, the basic molecular diagnostic techniques are discussed. In addition, the emerging ethical debate surrounding the use of this new technology is summarized. Caution is necessary when DNA tests are being used, especially in presymptomatic situations.

Neurofibromatosis: a common neurocutaneous disorder.

Neurofibromatosis (NF) type 1 (NF-1) is one of the most common of the neurocutaneous conditions, whereas NF type 2 (NF-2) accounts for an extremely small percentage of the total cases of NF. Indeed, most physicians will probably encounter at least one or two patients with NF-1 during the course of their practice. The manifestations can be varied and subtle; thus, the condition can sometimes be difficult to recognize. Nonetheless, the diagnosis of NF-1 is often clinically possible by the time the person is 10 years old. In this article, the diagnostic criteria for the most common types of NF are discussed, the common and some of the serious manifestations of both NF-1 and NF-2 are described, and suggestions for follow-up care are offered. Of importance, physicians must recognize that, although NF-1 and NF-2 share a common name, they are due to mutations in two different genes. Cure is not yet possible; thus, treatment is primarily symptomatic. A multi-disciplinary treatment team is often helpful, particularly for patients with complicated problems.

von Hippel-Lindau disease.

An autosomal dominant tumor predisposition syndrome, von Hippel-Lindau disease (VHL) is characterized by the presence of benign and malignant tumors. Hallmark lesions include retinal angiomas, hemangioblastomas of the cerebellum and spinal cord, and renal cell carcinomas. Affected persons may also have angiomatous or cystic lesions of the kidneys, pancreas, and epididymis, as well as adrenal pheochromocytomas. In this article, we discuss the clinical features and diagnostic criteria for this clinically underdiagnosed condition. An update on recent findings regarding the molecular genetics of VHL is provided, including a discussion of the evolving understanding of genotype-phenotype correlations. Understanding the molecular and functional aspects of this condition will lead to the development of strategies for the management and treatment of inherited and sporadic VHL-associated tumors.

Fluorescent in situ hybridization: use of whole chromosome paint probes to identify unbalanced chromosome translocations.

By identifying structural chromosome anomalies, the clinical cytogenetics laboratory can play a critical role in the diagnosis and treatment of patients with birth defects. Although many new staining techniques have been developed throughout the years to aid in the detection of anomalous chromosomes, some abnormalities still pose a special challenge to cytogeneticists. This difficulty is especially evident in patients with an abnormal chromosome that does not produce a recognizable banding pattern by conventional staining techniques. We describe a recently discovered method of identifying chromosomes by using whole chromosome-specific DNA probes and fluorescent in situ hybridization and provide examples of how this new procedure facilitated the identification of chromosome abnormalities in two patients with multiple birth defects.

Jarcho-Levin syndrome: four new cases and classification of subtypes.

The Jarcho-Levin syndrome is a condition manifested by vertebral body and related rib malformations. We report on four new cases and review 57 cases from the literature. Analysis of the 61 cases suggests that there are two major subtypes (spondylocostal dysostosis and spondylothoracic dysostosis) with different survival rates, associated malformations, and inheritance patterns. Individuals with spondylothoracic dysostosis have vertebral body malformations and ribs which flare in a fanlike pattern but which are not significantly malformed. This is an autosomal recessive trait, and the patients have a higher mortality rate and greater incidence of neural tube defects. Individuals with spondylocostal dysostosis have vertebral malformations, frequent dramatic rib malformations, and short stature, but do not have a fanlike thoracic configuration. Most cases of spondylocostal dysostosis are inherited in an autosomal recessive fashion, although in a few families it is a dominant trait which is correlated with better survival. Respiratory compromise previously accounted for the high mortality in these conditions, but improvements in respiratory technology have increased survival. Appropriate classification of these similar phenotypes will improve counseling concerning recurrence risk, management, and prognosis.

De Barsy syndrome: report of a case, literature review, and elastin gene expression studies of the skin.

Several "progeroid" syndromes have now been identified. The De Barsy syndrome is an autosomal recessive syndrome of dwarfism, mental deficiency, an "aged" appearance at birth, abnormal elastic fibers on skin biopsy, and lax skin, large helices, eye abnormalities, lax joints, hypotonia, and athetoid posturing. We report one case and review 11 cases from the literature. To understand the abnormal appearance of the elastic fibers on biopsy, we performed elastin gene expression studies on fibroblasts cultured from our patient's skin. Molecular hybridization studies revealed reduced elastin mRNA steady-state levels as compared with age matched control individuals. Assuming normal rates of mRNA translation, reduced elastin synthesis would occur. Diminished dermal elastin content could explain the altered cutaneous elasticity, decreased elastic fibers in the skin, and many clinical manifestations of individuals with this condition.

New skeletal dysplasia with unique brachydactyly.

We report on 2 male propositi, their mothers, and a maternal aunt with a new skeletal dysplasia associated with a unique pattern of digital malformation, variable mild short stature, and mild bowleg with proximal overgrowth of the fibula. The digital malformations comprise a pattern of brachydactyly which includes short, abducted thumbs, short index fingers, and markedly short, abducted great toes. The radiographic findings include hypoplastic thumbs and great toes with short first metacarpals and first metatarsals, absent distal phalanges of the index fingers and second toes, and coalescence of the carpal and tarsal bones. Radiographs of the long bones show mild metaphyseal and epiphyseal irregularity, tibial spurs, and relative elongation of the fibulae. The males are very similarly affected whereas the females show phenotypic variation and are generally less severely affected. The family histories from 2 fairly extensive pedigrees suggest X-linked dominant inheritance.

Familial recurrence of tracheoesophageal fistula and associated malformations.

Tracheoesophageal fistula (TEF) may occur as an isolated malformation or together with other malformations. To determine the recurrence risk of TEF or associated malformations in children and sibs, and to determine the frequency of associated malformations in index patients, we reviewed the Mayo Clinic records of 204 patients with TEF. Also, questionnaires were sent to patients or relatives. Questions were designed to determine whether the patient and relatives had TEF and/or related organ system (including VACTERL) malformations. The VACTERL association is a disorder characterized by 3 or more of the following: vertebral, anal, cardiac, renal, or radial anomalies, and TEF. One hundred twenty-eight families returned a completed questionnaire, and 140 index patients were ascertained based on complete medical records, questionnaire, and/or autopsy. Forty-one (29.3%) of 140 index patients had TEF with one other VACTERL malformation, and twenty-four (17.1%) of 140 index patients had TEF with at least two other VACTERL malformations. Of the 347 sibs of index patients, 5 (1.4%) had one VACTERL malformation each, including 1 sib with esophageal atresia (EA) without TEF. Of the 41 children of index patients, 1 (2.4%) had TEF plus two other VACTERL malformations; another had one non-TEF VACTERL malformation. From our study, the largest reported population of TEF patients to date, we conclude that: 1) nearly half (46%) of patients with tracheoesophageal fistula will exhibit other VACTERL malformations; 2) the recurrence risk for individuals with TEF to have affected children is 2-3%; and 3) there is an increased risk to relatives of TEF patients to exhibit other VACTERL malformations.

Uniparental disomy in congenital disorders: a prospective study.

Whole chromosome uniparental disomy (UPD) for several different chromosomes has been described in individuals with phenotypes that encompass a broad range of abnormalities. We prospectively searched for UPD in 25 cytogenetically normal individuals who had one or more of the following features: nonsyndromic multiple congenital anomalies, short stature, mental retardation, or dysmorphic findings. Using highly polymorphic microsatellite repeats, biparental inheritance of at least one locus on every chromosome was found in every individual and uniparental inheritance was not detected at any locus. If UPD does exist in this clinical setting, its frequency is less than 13.7% (95% confidence interval). Our data indicate that additional studies will be required to determine the true incidence of UPD in this population.

Establishment of a rhabdoid tumor cell line with a specific chromosomal abnormality, 46,XY,t(11;22)(p15.5;q11.23).

The malignant rhabdoid tumor is a rare, poorly understood tumor which occurs primarily in children. The kidney is a frequent primary site of origin, but the tumor has arisen in other mesodermally derived tissues as well. Controversy exists regarding the embryonic origin of the rhabdoid tumor and recent histopathologic studies suggest that it may be of neuroepithelial origin. Our immunohistochemical and electron micrographic studies support this theory. No consistent chromosome abnormalities have been reported in this tumor and no cell lines are available for study. We have established and characterized the first rhabdoid tumor cell line. It possesses a specific chromosomal abnormality, 46,XY,t(11;22)(p15.5;q11.23). The translocation may provide an important clue to the pathogenesis of the tumor as well as an opportunity for further study of the involved chromosome regions.

Cytogenetic analysis of 39 pediatric central nervous system tumors.

Consistent cytogenetic abnormalities have been described in many pediatric solid tumors, including Ewing's sarcoma, Wilms' tumor, and neuroblastoma. Similar analysis of pediatric central nervous system (CNS) tumors has been hampered by technical problems. We report chromosome results from 39 pediatric CNS tumors. Abnormalities of chromosome 17 were noted in 3 of 11 primitive neuroectodermal tumors (including i(17q) in 2 tumors), confirming data observed by other investigators. Cells from 2 of 11 primitive neuroectodermal tumors (PNET) exhibited loss or structural abnormalities involving chromosome 11. Loss or distal deletion of chromosome 7q was noted in cells from two PNETs. Because other investigators have shown loss of heterozygosity on 17p in about one-third of PNET, we propose that chromosome regions 7q and 11 are areas worthy of further study in pediatric PNET. Numerical abnormalities were noted in 6 of 21 astrocytomas. Hyperdiploidy was demonstrated in 1 of 4 pilocytic astrocytomas and pseudopolyploidy was demonstrated in 4 of 13 anaplastic astrocytomas. Structural chromosome abnormalities (translocations, deletions) were noted in 4 of 13 anaplastic astrocytomas. Complex structural anomalies were observed in one craniopharyngioma. A rhabdoid tumor of the brain exhibited multiple complex structural rearrangements but did not exhibit the monosomy 22 observed in some rhabdoid tumors. Hypodiploidy and loss of chromosome 22 were noted in a clinically aggressive meningioma, corroborating observations by other investigators.

The revolution in clinical genetics. Practical applications.

Recent advances in genetics directly affect family physicians. Many diagnostic tests are currently available to screen the fetus for malformations and genetic diseases, and gene therapy is slowly becoming a reality. This article discusses some of the screening techniques available, including chromosome analysis, ultrasound, and DNA studies.

Craniofacial and dental manifestations of Proteus syndrome: a case report.

The Proteus syndrome is a rare congenital hamartomatous condition that is characterized by a wide range of malformations, sometimes involving the face. Common manifestations include partial gigantism, congenital lipomas, and plantar hyperplasia. In this report we describe the craniofacial clinicopathological development in a girl with Proteus syndrome from age 6 to 20 years. The patient had pronounced hemifacial hypertrophy, exostoses in the left parietal region, and enlargement of the inferior alveolar nerve and mandibular canal in the affected region. The dental development of the affected left mandible and maxilla was characterized by extremely premature development and eruption of the primary and permanent teeth and by pronounced idiopathic root resorptions. The multidisciplinary management of the patient and the treatment outcome is reported. A review of the Proteus patients in the literature who exhibited manifestation in the craniofacial region is presented.

Mosaic trisomy 16 in a thriving infant: maternal heterodisomy for chromosome 16.

Trisomy 16 is the most common trisomy in spontaneous abortions and is usually, if not always, lethal in the nonmosaic state. We report a liveborn infant with trisomy 16 mosaicism first diagnosed by amniocentesis at 20 weeks gestation. At birth, the infant was growth retarded and mildly dysmorphic. At age 14 months she was developmentally normal and had facial asymmetry. Her length, weight and head circumference were normal. Pure trisomy 16 was found in cells from the placenta. A normal female karyotype was found in lymphocytes from the infant. Skin fibroblasts revealed a trisomy 16 karyotype in 6 of 30 cells. Molecular analysis showed maternal uniparental heterodisomy, indicating that the trisomic conceptus arose from a nondisjunction of maternal meiosis. Fibroblasts may be the tissue of choice for detection of low-level trisomy 16 mosaicism.