Prevalence of lens changes in Ukrainian children residing around Chernobyl

The objective of this study is to determine the prevalence and characteristics of lens changes in the eyes of a pediatric population, 5-17 y old, living in the permanent control zone around the Chernobyl nuclear reactor and to compare these findings with those from an unexposed control population. A total of 1,787 children are reported on (996 exposed and 791 unexposed). Over three-quarters of the subjects examined in this study show a form of minor change, termed focal lens defect, in the cortical and/or nuclear portions of the lens of the eye. The exposed group shows a small (3.6%), but statistically significant excess (p = 0.0005) of subclinical posterior subcapsular lens changes similar in form to changes identified in atomic bomb survivors. These posterior subcapsular changes tend to occur in boys 12-17 y old and in exposed children who report consuming locally grown mushrooms on a regular basis.

Sequence analysis and exclusion of phosducin as the gene for the recessive retinal degeneration of the Abyssinian cat

Phosducin was evaluated as a candidate gene for the recessive retinal degeneration in the Abyssinan cat, rdAc, using reverse transcription and polymerase chain amplification. The nucleotide sequence of the cat phosducin coding region was determined except for 23 bp at the 5' end. Single-strand conformation analysis of a silent polymorphism within the coding region established the nonlinkage of the phosducin gene with the rdAc locus.

A peripherin/retinal degeneration slow mutation (Pro-210-Arg) associated with macular and peripheral retinal degeneration

BACKGROUND

Mutations in the peripherin/retinal degeneration slow (RDS) gene have been identified in patients with retinitis pigmentosa and pattern macular dystrophy. The authors initially examined a large family affected with both peripheral and macular degeneration, inherited as an autosomal dominant trait. Screening for peripherin/RDS mutations identified a previously unreported nucleotide alteration in all of the affected individuals. Two additional families later were found to have this same mutation.

METHODS

DNA samples from the members of three unrelated families were screened for peripherin/RDS mutations by denaturing gradient gel electrophoresis of the polymerase chain reaction-amplified peripherin/RDS coding sequences. The sequence change that was detected was further characterized by DNA sequencing. Family members were examined and evaluated with psychophysical and electrophysiologic methods.

RESULTS

A proline to arginine mutation in codon 210 of peripherin/RDS was found in all clinically affected individuals. Macular changes included extensive geographic atrophy, pigment epithelial changes, and/or drusen. The proline to arginine mutation was not found among 100 healthy individuals, making it unlikely to be a nondisease-causing polymorphism.

CONCLUSIONS

The authors identified a novel peripherin/RDS gene mutation associated with autosomal dominant retinal degeneration in patients from three different families. The largest family showed a broad variability in the expressivity of the mutation. The overlap of clinical features with those of age-related maculopathy highlights the need to consider photoreceptor-specific genes as potential factors in the etiology of the latter condition.

Clinical diversity and chromosomal localization of X-linked cone dystrophy (COD1)

X-linked progressive cone dystrophy (COD1) causes progressive deterioration of visual acuity, deepening of central scotomas, macular changes, and bull's-eye lesions. The cone electroretinography (ERG) is variably abnormal in affected males, and the rod ERG may also be abnormal. The clinical picture of heterozygous females ranges from asymptomatic to a widespread spectrum of cone-mediated dysfunction. A prior linkage study demonstrated linkage between the COD1 locus and the marker locus DXS84, assigned to Xp21.1, with no recombination. In the present study, we have clinically characterized a large four-generation family with COD1 and have performed a linkage analysis using seven polymorphic markers on the short arm of the X chromosome. No recombination was observed between the disease and the marker loci DXS7 and MAOA, suggesting that the location of COD1 is in the region Xp11.3, distal to DXS84 and proximal to ARAF1.

Angioid streaks associated with abetalipoproteinemia

Angioid streaks were observed in two patients with abetalipoproteinemia. The progression of the angioid streaks was minimal over the years that these patients received vitamin A and E supplementation, though in one patient the development of subretinal neovascular membranes within the angioid streaks was the cause of rapid central visual loss. The simultaneous appearance of two rare entities in unrelated individuals strengthens the relationship between these two disorders that has been suggested by previous case studies. The authors propose a common metabolic pathway involving trace element deficiencies that may account for this relationship as well as the association of angioid streaks with other rare disorders such as Paget's disease, hypoparathyroidism, lead poisoning, hyperphosphatemia, and a number of hemoglobinopathies. Their study of these two patients underscores the need for further investigations as to the role of copper, zinc and omega-3 fatty acids in the pathogenesis of retinopathy in abetalipoproteinemia.

Efficient strategies for genomic searching using the affected-pedigree-member method of linkage analysis

The affected-pedigree-member (APM) method of linkage analysis is a nonparametric statistic that tests for nonrandom cosegregation of a disease and marker loci. The APM statistic is based on the observation that if a marker locus is near a disease-susceptibility locus, then affected individuals within a family should be more similar at the marker locus than is expected by chance. The APM statistic measures marker similarity in terms of identity by state (IBS) of marker alleles; that is, two alleles are IBS if they are the same, regardless of their ancestral origin. Since the APM statistic measures increased marker similarity, it makes no assumptions concerning how the disease is inherited; this can be an advantage when dealing with complex diseases for which the mode of inheritance is difficult to determine. We investigate here the power of the APM statistic to detect linkage in the context of a genomewide search. In such a search, the APM statistic is evaluated at a grid of markers. Then regions with high APM statistics are investigated more thoroughly by typing more markers in the region. Using simulated data, we investigate various search strategies and recommend an optimal search strategy that maximizes the power to detect linkage while minimizing the false-positive rate and number of markers. We determine an optimal series of three increasing cut-points and an independent criterion for significance.

Genetic heterogeneity of Usher syndrome type II

Usher syndrome is an autosomal recessive disorder characterised by retinitis pigmentosa and congenital sensorineural hearing loss. A gene for Usher syndrome type II (USH2) has been localised to chromosome 1q32-q41. DNA from a family with four of seven sibs affected with clinical characteristics of Usher syndrome type II was genotyped using markers spanning the 1q32-1q41 region. These included D1S70 and D1S81, which are believed to flank USH2. Genotypic results and subsequent linkage analysis indicated non-linkage of this family to these markers. The A test analysis for heterogeneity with this family and 32 other Usher type II families was statistically significant at p < 0.05. Further clinical evaluation of this family was done in light of the linkage results to determine if any phenotypic characteristics would allow for clinical identification of the unlinked type. No clear phenotypic differences were observed; however, this unlinked family may represent a previously unreported subtype of Usher type II characterised by a milder form of retinitis pigmentosa and mild vestibular abnormalities. Heterogeneity of Usher syndrome type II complicates efforts to isolate and clone Usher syndrome genes using linkage analysis and limits the use of DNA markers in early detection of Usher type II.

Sequence-specific scission of DNA by RNAs linked to a chemical nuclease

RNAs linked to the chemical nuclease 1,10-phenanthroline-copper cut double-stranded DNA of complementary sequence. This cleavage reaction is applicable to all sequences and can be used to measure the distance between marker genes in base pairs, map the size of a transcription unit and define positions of chromosomal breakpoints.

Sequence-specific scission of DNA by the chemical nuclease activity of 1,10-phenanthroline-copper(I) targeted by RNA

RNAs modified with the chemical nuclease 1,10-phenanthroline-copper(I) can achieve the sequence-specific scission of single- and double-stranded DNA targets. The RNAs are prepared in vitro by using 5-(3-aminoallyl)-UTP as the sole source of UTP and can be readily modified with 1,10-phenanthroline by using N-succinimidyl 3-(2-pyridyl-dithio)propionate (SPDP) to cross-link the ligand to the aminoallyl moiety. Single-stranded DNAs are efficiently cleaved at multiple sites because 1,10-phenanthroline is incorporated at several uridines in the sequence. Sequence-specific double-stranded scission of duplex DNA can also be accomplished with 1,10-phenanthroline-derivatized RNA within R loops. These triple-stranded structures form in 70% formamide and involve the displacement of one strand of DNA by the RNA of identical sequence. R loop-directed scission is the first method for DNA scission applicable to any sequence. A unique application of R loop-targeted nucleolytic scission, which relies on its ability to cut DNA at any sequence, is the determination of the distance between two marker DNA sequences within a target. In this case, 1,10-phenanthroline-linked RNAs are prepared from the two distinct sequences and used to cut the DNA fragment after R-loop formation. The size of the fragment liberated by these methods is a direct measure in base pairs of the distance between the two DNA sequences. For example, the distance separating two chicken delta crystallin (delta 1 and delta 2) genes has been confirmed as 24 kilobases by this method.

Broad-spectrum Möbius syndrome associated with a 1;11 chromosome translocation

The authors report a case of Möbius syndrome with Poland syndrome, cleft palate, dextrocardia, mandibular hypoplasia, and multiple areas of diffuse brain volume loss. Karyotype demonstrated a t(1;11)(p22;p13) translocation in the patient and his phenotypically normal father and brother. This case extends the spectrum of congenital disorders that are associated with Möbius syndrome and raises the possibility of genetic heterogeneity for the Möbius disorder.

Mus spretus-specific LINE-1 DNA probes applied to the cloning of the murine pearl locus

LINE-1 is the major family of long, interspersed, repetitive DNA sequences found in mammalian genomes. The mouse species Mus spretus contains large LINE-1 subfamilies that are distinguishable from the LINE-1 elements of laboratory Mus domesticus strains by their content of particular nucleotide differences. Oligonucleotides containing these differences act as M. spretus-specific LINE-1 hybridization probes. We have used these probes as a novel genetic tool in conjunction with an interspecific hybrid congenic mouse, in which the M. spretus allele of the pearl gene has been transferred onto a M. domesticus background. From a lambda library prepared from this congenic mouse, four clones were isolated by hybridization to the M. spretus-specific probes. After derivation of genetic markers from these clones, two of them were found to be linked to the pearl gene. These markers are the first two of up to 75 that could be isolated to support cloning the pearl gene. Considering the interspersed nature of LINE-1, we propose that species-specific LINE-1 probes could also be used to isolate markers for many other target genes.

Screening for von Hippel-Lindau disease by DNA polymorphism analysis

OBJECTIVE

Von Hippel-Lindau (VHL) disease is a rare, inherited multisystem neoplastic disorder. There is no biochemical test available to distinguish VHL disease gene carriers from their healthy siblings. We evaluated DNA polymorphism analysis as a method for identifying disease gene carriers.

DESIGN

Prospective comparison of the results of DNA analysis with a comprehensive clinical screening examination.

SETTING

The Clinical Center of the National Institutes of Health.

PATIENTS

Blood was collected from 182 members of 16 families with VHL disease. Forty-eight asymptomatic individuals, at risk of developing this hereditary illness (with an affected parent or sibling), were examined for occult disease at the Clinical Center of the National Institutes of Health and tested by DNA polymorphism analysis.

RESULTS

DNA polymorphism analysis predicted nine disease gene carriers and 33 individuals with the wild-type (normal) allele among the 48 individuals at risk of developing VHL disease; the test was not informative in six individuals. All nine individuals predicted to carry the VHL gene had evidence of occult disease on clinical examination. There was no clinical evidence of VHL disease in 32 of 33 individuals predicted to carry the wild-type allele.

CONCLUSIONS

DNA polymorphism analysis can identify individuals likely to carry the VHL disease gene among asymptomatic members of disease families. This technique serves to focus attention on those individuals who require periodic medical examination and may help to alleviate the morbidity and mortality associated with this disease.

Von Hippel-Lindau (VHL) disease: distinct phenotypes suggest more than one mutant allele at the VHL locus

As part of an attempt to locate the von Hippel-Lindau locus (VHL) on chromosome 3, we evaluated 41 families with von Hippel-Lindau disease from the United States and Canada. One large family was identified whose disease phenotype was distinct from typical VHL. The most common disease manifestation was pheochromocytoma occurring in 57% (27/47) of affected family members. Few (4/47) affected family members had symptomatic spinal or cerebellar hemangioblastomas; no affected family member had renal cell carcinoma (0/47) or pancreatic cysts (0/24). Previously, genetic analysis demonstrated that the disease manifestations in this family were linked to RAF1 and D3S18, markers shown to be linked to typical VHL. These results suggest that there are mutant alleles at the VHL locus associated with distinct tissue specificities.

Central nervous system involvement in Von Hippel-Lindau disease

Fifty individuals with Von Hippel-Lindau disease (VHL) were studied with gadolinium-enhanced magnetic resonance imaging (MRI) to determine the frequency and distribution of CNS lesions. The associated clinical features were also reviewed. Thirty-six (72%) of the 50 had 1 or more CNS tumors. The most frequently affected sites in the CNS excluding the retina were the cerebellum (52%), spinal cord (44%), and brainstem (18%). New regional predilections for the craniocervical junction and conus medullaris were demonstrated by this study. Forty-one percent of all VHL patients with CNS tumors were neurologically asymptomatic: cerebellar tumors (50%), spinal cord tumors (50%), and brainstem tumors (44%) were often without clinical signs or symptoms. Multiple lesions were common. The mean age of all VHL patients (34.5 years) was similar to the mean age of all CNS VHL patients (34.4 years), suggesting a lack of age association. CNS lesions commonly occurred in the 2nd decade of life. All patients at risk for VHL should be evaluated using gadolinium-enhanced MRI after 10 years of age, although ophthalmic examination should be initiated within the 1st 2 years of life. Enhanced MRI is particularly useful in the detection of CNS tumors in patients with the VHL gene.

von Hippel-Lindau disease: radiologic screening for visceral manifestations

The visceral manifestations of von Hippel-Lindau (VHL) disease can cause significant morbidity and mortality. The authors prospectively screened 37 persons from a single kindred. Twenty-five subjects underwent abdominal ultrasound (US), contrast material-enhanced abdominal computed tomography (CT), and nonenhanced abdominal magnetic resonance (MR) imaging. Eight subjects younger than 16 years of age underwent abdominal US and MR imaging only. Scrotal US was employed in 25 male patients. Eleven subjects had renal cysts or tumors. Contrast-enhanced CT depicted renal abnormalities in 10 of these subjects, US in seven, and MR imaging in nine. Among 12 subjects with pancreatic cysts or tumors, CT showed pancreatic abnormalities in all 12, US in nine, and MR imaging in nine. Three subjects (mean age, 34.5 years) had renal tumors, and three had pancreatic masses. Scrotal US revealed epididymal cystadenomas in seven subjects; two of these tumors were surgically verified. A combination of contrast-enhanced CT and scrotal US in male patients appears to be the best way to screen for visceral manifestations of VHL disease.

Radiologic screening for von Hippel-Lindau disease: the role of Gd-DTPA enhanced MR imaging of the CNS

Thirty-seven members of a family with von Hippel-Lindau disease (VHL) were prospectively screen for CNS hemangioblastomas; 10 family members were previously known to have VHL. Radiographic studies included noncontrast magnetic resonance (MR) imaging of the head (all patients) and spine (34 patients) and contrast-enhanced CT (CCT) of the head (all adult patients). Eleven patients had Gd-DTPA enhanced MR (CMR) of the head and 10 patients had CMR of the spine. Sixteen patients had radiographic evidence of CNS hemangioblastomas and all but six patients were symptomatic. Using comparable studies, CMR of the head demonstrated more lesions than the other modalities (31, 22, and 19 for CMR, MR, and CCT, respectively). Furthermore, CMR better separated tumor from edema, as well as cystic from solid components. Contrast enhanced MR was superior to noncontrast MR of the spine in lesion detection (31 vs. 4; p less than 0.001). Noncontrast MR was particularly limited in four patients with syringomyelia. We conclude that postcontrast MR of the head and spine is the best currently available means of detecting hemangioblastomas associated with VHL.

Detection of the carrier state of X-linked retinoschisis

We determined the extent of suppressive rod-cone interaction in 11 obligate carriers and eight potential carriers of X-linked retinoschisis from eight families. Despite otherwise normal ophthalmoscopic and functional testing, all of the obligate heterozygous carriers demonstrated a complete absence of normal rod-cone interaction. Of the potential heterozygous carriers, three had normal rod-cone interactions, two had no detectable interaction, and two yielded technically unsatisfactory results. This lack of rod-cone interactions allows heterozygous individuals to be identified clinically and has implications concerning the origin of this inherited disorder.

Genetic linkage analysis of autosomal dominant congenital cataracts with lens-specific DNA probes and polymorphic phenotypic markers

The authors studied a four-generation family with autosomal dominant congenital cataracts (ADCCs) using linkage analysis with 23 polymorphic phenotypic markers and DNA restriction fragment length polymorphisms (RFLPs) detected by lens-specific DNA probes. A total of 19 family members were studied and the ten affected members had embryonal lens opacities. Close linkage was rejected with DNA probes encoding beta-crystallin, gamma-crystallin, and the major intrinsic protein of the lens fiber membrane (MIP) excluding defects of these genes as the cause of the cataract in this family. No statistically significant lod scores were produced with the polymorphic phenotypic markers. These results support the genetic heterogeneity of ADCCs.

Nucleotide sequence for the cDNA of the bovine beta B2 crystallin and assignment of the orthologous human locus to chromosome 22

We have identified and characterized two over-lapping bovine cDNA clones corresponding to the bovine crystallin beta Bp. The longer of the two clones, which contains the entire coding and 3' untranslated region as well as 54 nucleotides of the 5' untranslated sequence was used to identify and map an orthologous human gene, Hu beta B2, to chromosome 22, q11.2-q12.2. As one other human beta-crystallin, Hu beta A3/A1, has been mapped to chromosome 17, our results indicate that, unlike the tightly linked gamma-crystallins, the human beta-crystallins are not syntenic within the genome.

Assignment of a human beta-crystallin gene to 17cen-q23

The gene map assignment of a human beta-crystallin gene to 17cen-q23 has been made using a bovine probe in the study of human-mouse and human-Chinese hamster somatic cell hybrids containing parts of human chromosome 17.

The gene for the major intrinsic protein (MIP) of the ocular lens is assigned to human chromosome 12cen-q14

The gene for the human major intrinsic protein (MIP) of the ocular lens fiber membrane has been assigned to region cen-q14 of chromosome 12 through the use of somatic cell hybrids containing the whole chromosome and parts of human chromosome 12.

The major intrinsic protein (MIP) of the bovine lens fiber membrane: characterization and structure based on cDNA cloning

Synthetic oligonucleotide probes have been used to identify two overlapping cDNA clones that represent the entire coding region of the mRNA for the major intrinsic protein (MIP) of bovine lens cell membrane. Hybridization studies indicate that bovine MIP is encoded by a single-copy gene. The cDNA hybridizes to the rat genome, but MIP mRNA is not detected in rat liver. Analysis of the deduced amino acid sequence provides support for the potential role of MIP as a junctional protein. The structure predicted for MIP suggests that it traverses the lipid bilayer six times with both carboxy and amino termini on the cytoplasmic side, and that it has at least one amphiphilic transmembrane segment, as expected if the protein were to participate in the formation of an aqueous channel.

The evolution of alpha-fetoprotein and albumin. II. The structures of the alpha-fetoprotein and albumin genes in the mouse

The murine alpha-fetoprotein (AFP) and albumin genes have been cloned from genomic libraries derived from Balb/c DNA. By restriction endonuclease mapping and electron microscopy, we have shown that both genes are organized similarly into 15 coding segments interrupted by 14 intervening sequences. The sizes of the corresponding coding segments in each gene are identical, lending support to the hypothesis that the two genes, were derived from a common ancestral gene. However, no nucleotide homology between coding segments was observed. Both the sizes and the nucleotide sequence of flanking and intervening sequences have diverged significantly as well. Two regions of the AFP gene, 925 base pairs in the 5' flanking DNA and 180 base pairs in the third intervening sequence, hybridized to the same region of DNA in the third intervening sequence of albumin. The 180-base pair homologies within each gene are present in opposite orientation relative to the direction of transcription, and are associated with reiterated DNA. Thus, it is unlikely that they represent true sequence conservation. An examination of the sizes of the coding segments in each gene reveals a thrice repeated domain, consisting of 4 coding segments. We propose that these correspond to the three domains observed in several mammalian albumins, and in murine AFP.