The status of the gene map of the human chromosomes.

In man, the specific chromosome that carries each of about 210 gene loci is known. These loci include at least one assigned to each chromosome (including the Y), about 110 assigned to specific autosomes, and about 100 to the X chromosome. For many loci, information on regional chromosomal localization is also available. The information comes mainly from studies in families and somatic cell hybrids, as well as an intgratsight of results from the two methods. Knowledge of the chromosome map gives insight into evolution, chromosomal organization in relation to genetic control mechanisms, and the pathogenesis of neoplasms and malformations. Furthermore, it is useful in prenatal or premorbid diagnosis of hereditary diseases.

Defect in conversion of procollagen to collagen in a form of Ehlers-Danlos syndrome.

Three patients with a form of the Ehlers-Danlos syndrome, a generalized disorder of connective tissue, have detectable amounts of procollagen in extracts of their skin and tendon. The activity of procollagen peptidase, the enzyme that converts procollagen to collagen, is reduced in cultures of fibroblasts. The clinical manifestations of this syndrome may be related to impaired enzymatic conversion of procollagen to collagen. Cultures of skin fibroblasts from these patients have an increased rate of synthesis of collagenous protein (collagen and procollagen), possibly related to the inability of these cells to convert procollagen to collagen.

Genetic characteristics of the HeLa cell.

The genotype of the patient Henrietta Lacks from whose cervical carcinoma the HeLa cell was derived was deduced from the phenotypes of her husband and children, and from studies of the HeLa cell. Hemizygous expression of glucose-6-phosphate dehydrogenase in HeLa, together with the deduced heterozygosity of Mrs. Lacks, is consistent with clonal origin of her neoplasm.

The sequence of the human genome.

A 2.91-billion base pair (bp) consensus sequence of the euchromatic portion of the human genome was generated by the whole-genome shotgun sequencing method. The 14.8-billion bp DNA sequence was generated over 9 months from 27,271,853 high-quality sequence reads (5.11-fold coverage of the genome) from both ends of plasmid clones made from the DNA of five individuals. Two assembly strategies-a whole-genome assembly and a regional chromosome assembly-were used, each combining sequence data from Celera and the publicly funded genome effort. The public data were shredded into 550-bp segments to create a 2.9-fold coverage of those genome regions that had been sequenced, without including biases inherent in the cloning and assembly procedure used by the publicly funded group. This brought the effective coverage in the assemblies to eightfold, reducing the number and size of gaps in the final assembly over what would be obtained with 5.11-fold coverage. The two assembly strategies yielded very similar results that largely agree with independent mapping data. The assemblies effectively cover the euchromatic regions of the human chromosomes. More than 90% of the genome is in scaffold assemblies of 100,000 bp or more, and 25% of the genome is in scaffolds of 10 million bp or larger. Analysis of the genome sequence revealed 26,588 protein-encoding transcripts for which there was strong corroborating evidence and an additional approximately 12,000 computationally derived genes with mouse matches or other weak supporting evidence. Although gene-dense clusters are obvious, almost half the genes are dispersed in low G+C sequence separated by large tracts of apparently noncoding sequence. Only 1.1% of the genome is spanned by exons, whereas 24% is in introns, with 75% of the genome being intergenic DNA. Duplications of segmental blocks, ranging in size up to chromosomal lengths, are abundant throughout the genome and reveal a complex evolutionary history. Comparative genomic analysis indicates vertebrate expansions of genes associated with neuronal function, with tissue-specific developmental regulation, and with the hemostasis and immune systems. DNA sequence comparisons between the consensus sequence and publicly funded genome data provided locations of 2.1 million single-nucleotide polymorphisms (SNPs). A random pair of human haploid genomes differed at a rate of 1 bp per 1250 on average, but there was marked heterogeneity in the level of polymorphism across the genome. Less than 1% of all SNPs resulted in variation in proteins, but the task of determining which SNPs have functional consequences remains an open challenge.

Diabetes mellitus and sexual ateliotic dwarfism: a comparative study.

The incidence of diabetic retinopathy was determined in 38 diabetics and 31 sexual ateliotic dwarfs deficient only in human growth hormone (HGH). The age and sex distribution were approximately the same in each group. The incidence and pattern of glucose intolerance were similar in diabetics and HGH-deficient dwarfs. The majority of diabetics (21 of 38) and HGH-deficient dwarfs (26 of 31) exhibited insulinopenia after glucose, mixed glucose-beef meals, and the infusion of l-arginine. A smaller number of HGH-deficient dwarfs (5 of 31) and diabetics (8 of 38) had normal or augmented absolute insulin responses to these same provocative stimuli. Hypercholesterolemia and hypertriglyceridemia occurred with greater frequency in both diabetics and HGH-deficient dwarfs than in normal controls. 8 of 21 diabetics and 6 of 21 sexual ateliotics exhibited significant hypertriglyceridemia. Five diabetics and six sexual ateliotics had significantly greater than normal serum cholesterol levels. Nearly half of the diabetics (16 of 38) had significant pathological abnormalities of the retina, but these changes were conspicuously absent in HGH-deficient dwarfs. No retinal lesions were detected in any HGH-deficient dwarf.

Thrombocytopenia with absent radius (TAR).

Forty examples (27 from the literature and 13 new cases) of a syndrome of hypomegakaryocytic thrombocytopenia with bilateral absence of the radius have been analyzed. This syndrome is designated in this paper as "thrombocytopenia with absent radius (TAR)". The onset of hematologic complications usually occurs at birth or during early infancy. Thrombocytopenia may be episodic and sometimes is accompanied by leukemoid reactions and eosinophilia. Bone marrow examination reveals decreased and/or abnormal megakaryocytes, with normal myeloid and erythroid precursors. Congenital skeletal deformities include bilateral absence of radius, shortening and deformity of the ulnae, and occasionally absence of all the long bones in the arm. The fingers and thumbs are always present. Other skeletal anomalies are frequent. Cardiac anomalies, particularly the tetralogy of Fallot and atrial septal defects, may be present. Other non-skeletal congenital abnormalities are rare. The prognosis is good if the patient survives to one year of age. The syndrome has been compared to Fanconi's anemia, thalidomide embryopathy, limb-cardiovascular syndrome, and a syndrome of multiple congenital malformations, from which it can be distinguished.

The anatomy of the human genome.

More than 350 genes have been assigned to specific chromosomes. These include more than 110 assigned to the X chromosome, more than 240 assigned to specific autosomes, and at least one assigned to the Y chromosome. (Even man's 25th chromosome, that of the mitochondrion, is being mapped). Almost all the assignments to specific autosomes were made in the last decade. About half of these were made by study of clones derived from interspecific (e.g., man-mouse) somatic cell hybrids. Over a fifth were made by family linkage studies. Chromosomes 1 and 6 are rather extensively mapped. The genes of over 40 autosomal disorders have been specifically localized. The comparative anatomy, functional anatomy, developmental anatomy and even applied anatomy of the human genome is becoming better known.

Fever with dissecting aneurysm of the aorta.

Following acute aortic dissection, it two of the four cases we describe the patients experienced a prolonged febrile syndrome which spontaneously resolved five and 11 weeks later. Because of fever and a murmur of aortic regurgitation, the two other patients with aortic dissection were initially treated for acute bacterial endocarditis. These four cases serve to re-emphasize fever as an important clinical manifestation of dissecting aneurysm of the aorta.

Echocardiographic assessment of cardiovascular abnormalities in the Marfan syndrome. Comparison with clinical findings and with roentgenographic estimation of aortic root size.

Echocardiographic abnormalities of the mitral valve and aortic root were compared with auscultatory findings and with assessment of aortic root size by chest roentgenography in 61 patients with the Marfan syndrome. Echocardiography was more sensitive than physical examination in detecting valvular and aortic root abnormalities. Although physical examination revealed findings of mitral valve disease and/or of aortic regurgitation in 52 percent of patients (mitral valve disease in 44 percent and aortic regurgitation in 23 percent), echocardiography detected abnormalities of the mitral valve and/or aortic root in 82 percent of patients (mitral valve prolapse in 57 percent and aortic root enlargement in 69 percent). Prevalence of mitral valve prolapse was approximately equal in male and female patients, whereas aortic root enlargement was more frequent in males (83 percent) than in females (50 percent). Echocardiographically detected aortic root enlargement was frequently not apparent on chest x-ray films. Indeed, five patients with markedly increased aortic root diameters (ranging from 6.0 to 7.9 cm) had no evident enlargement of the aortic root on routine chest x-ray films. In all four of those patients who had angiographic and/or pathologic correlations, confirmation of marked aortic root dilatation was obtained. There are limitations to echocardiographic evaluation of the presence and severity of underlying cardiovascular disease in patients with the Marfan syndrome. Mitral valve disease may not be detected, especially in patients with left ventricular dilatation. In addition, due to anteroposterior compression of the left atrium by the enlarged aorta, left atrial size may be underestimated in patients with aortic root enlargement.

Ehlers-Danlos syndrome with abnormal collagen fibrils, sinus of Valsalva aneurysms, myocardial infarction, panacinar emphysema and cerebral heterotopias.

A 30 year old woman with marked joint hypermobility had severe, progressive lung disease, seizures, aneurysms of the sinuses of Valsalva and myocardial infarction documented during life. She died of intractable ventricular fibrillation, and postmortem examination showed myocardial injury in the distribution of the left coronary artery but no occlusive coronary artery disease. Severe panacinar emphysema was found in the lungs. Cerebral heterotopias with peculiar vascularization were present and were a likely cause of the seizure disorder. Electron microscopy showed dermal collagen fibrils to be heterogeneous in size, reduced in number, and irregular and frayed in appearance. This patient had a form of the Ehlers-Danlos syndrome, different from the 10 distinct variants described thus far, associated with lethal internal manifestations.

The iduronidase-deficient mucopolysaccharidoses: clinical and roentgenorgraphic features.

Hurler and Scheie syndromes, two of the six clinically distinct mucopolysaccharidoses, are deficient in the same lysosomal enzyme, alpha-L-iduronidase. A third group of iduronidase-deficient patients can now be identified during the pediatric years using clinical and radiographic criteria. Based on inferential evidence for allelism between the Hurler and Scheie genes, the occurrence of genetic compounds which simultaneously carry both mutant alleles may be predicted to occur. This can be considered analogous to the structural gene mutations leading to hemoglobin SC disease. Four patients with phenotypes intermediate between Hurler and Scheie syndromes are flet to represent genetic compounds of this type. Both clinical and roentgenographic features are helpful in distinguishing these patients from those with Hurler syndrome or Scheie syndrome. Fibroblast correction characteristics identical to those of Hurler syndrome and Scheie syndrome and absence of consanguinity are additional features which favor classification as genetic compounds. The possibility of a third mutant allele at the Hurler-Scheie locus or of extreme phenotype variation are not considered likely alternative explantations. Depending on the frequency of the Scheie syndrome and the Hurler syndrome, genetic compounds may occur with an intermediate frequency or may be more common than either homozygous condition.

The association of Waardenburg syndrome and Hirschsprung megacolon.

We describe four patients with Waardenburg syndrome and Hirschsprung aganglionic megacolon. In view of pathophysiologic relationships and animal studies, we conclude that the association of these two uncommon disorders is pathophysiologically significant.

Gonadal mosaicism in pseudoachondroplasia.

We report on a family in which a brother and sister have pseudoachondroplasia and normal parents. The brother married a normal woman, and they have 2 daughters; one of them has typical changes of pseudoachondroplasia, the other is normal. The most likely explanation in this family is gonadal (germinal cell) mosaicism in one of the grandparents. Other reports of possible autosomal recessive pseudoachondroplasia are reviewed. It is likely that gonadal mosaicism is responsible for a small percentage of cases with what appears to be a new mutation for pseudoachondroplasia.

Deletion of PTEN in a patient with Bannayan-Riley-Ruvalcaba syndrome suggests allelism with Cowden disease.

We report on an 18-month-old boy with an interstitial deletion at 10q23.2-q24.1. This region includes the PTEN gene, mutations of which have been reported to cause Cowden disease. Our patient presented with manifestations of Bannayan-Riley-Ruvalcaba (BRR) syndrome. The BRR syndrome is a rare disorder which presents most commonly in childhood. Cowden disease is a disease of adulthood and is inadequately described in children. Because of the considerable phenotypic overlap between the two disorders, and the cytogenetic and molecular findings in our patient, we suggest that BRR syndrome and Cowden disease are allelic.

Small deletions in the type II collagen triple helix produce kniest dysplasia.

Kniest dysplasia is a moderately severe type II collagenopathy, characterized by short trunk and limbs, kyphoscoliosis, midface hypoplasia, severe myopia, and hearing loss. Mutations in the gene that encodes type II collagen (COL2A1), the predominant protein of cartilage, have been identified in a number of individuals with Kniest dysplasia. All but two of these previously described mutations cause in-frame deletions in type II collagen, either by small deletions in the gene or splice site alterations. Furthermore, all but one of these mutations is located between exons 12 and 24 in the COL2A1 gene. We used heteroduplex analysis to identify sequence anomalies in five individuals with Kniest dysplasia. Sequencing of the index patients' genomic DNA identified four new dominant mutations in COL2A1 that result in Kniest dysplasia: a 21-bp deletion in exon 16, an 18-bp deletion in exon 19, and 4-bp deletions in the splice donor sites of introns 14 and 20. A previously described 28-bp deletion at the COL2A1 exon 12-intron 12 junction, deleting the splice donor site, was identified in the fifth case. The latter three mutations are predicted to result in exon skipping in the mRNA encoded from the mutant allele. These data suggest that Kniest dysplasia results from shorter type II collagen monomers, and support the hypothesis that alteration of a specific COL2A1 domain, which may span from exons 12 to 24, leads to the Kniest dysplasia phenotype.

Profound first-degree atrioventricular block. A 30-year study.

We report the findings in a 60-year-old patient with a 30-year history of profound first-degree heart block with no associated cardiac abnormalities. The sinus node and the His-Purkinje system were normal. The time for atrioventricular nodal conduction was prolonged, with normal refractoriness both before and after administration of atropine, suggesting that the atrioventricular node may be lengthened, although electrically normal.