Leveraging natural diversity: back through the bottleneck.

Plant breeders have long recognized the existence of useful genetic variation in the wild ancestors of our domesticated crop species. In cultivated rice (Oryza sativa), crosses between high-yielding elite cultivars and low-yielding wild accessions often give rise to superior offspring, with wild alleles conferring increased performance in the context of the elite cultivar genetic background. Because the breeding value of wild germplasm cannot be determined by examining the performance of wild accessions, a phylogenetic approach is recommended to determine which interspecific combinations are most likely to be useful in a breeding program. As we deepen our understanding of how genetic diversity is partitioned within and between cultivated and wild gene pools of Oryza, breeders will have increased power to make predictions about the most efficient strategies for utilizing wild germplasm for rice improvement.

Placental 11ß-Hydroxysteroid dehydrogenase type 2 expression: Correlations with birth weight and placental metal concentrations.

INTRODUCTION: Infants born below 2500 g are classified as low birth weight. Excess in utero exposure to cortisol has been linked to restricted fetal growth. Placental production of 11ß-hydroxysteroid dehydrogenase type 2 (11ß-HSD2) inactivates cortisol before passage into the fetus. The present study tested the hypothesis that placental 11ß-HSD2 expression is positively correlated with an individualized birth weight centile and raw birth weight, and examines the relationship between metal concentrations in placental tissue and 11ß-HSD2 expression. METHODS: Placentae from 191 births were collected and samples preserved to maintain mRNA profile. Placental 11ß-HSD2 expression was measured via qRT-PCR. Addition samples were collected from placental tissues and uniformly dried in order to quantify 18 metals via ICP-MS (n = 160). RESULTS: A significant, positive correlation between 11ß-HSD2 expression and individualized birth weight centile (p = 0.0321) and birth weight (p = 0.0243) was found. Additionally, maternal age and gestational age were positivity correlated with each other (p = 0.0321). Birth weight was significantly different with race, marital status, education and maternal tobacco use. Four metals (Co, Mn, Ni, Zn) demonstrated significant positive correlations (p < 0.05) with 11ß-HSD2 expression. Sex specific differences were found; Co, Cu, Fe, Zn, and Ni were positively correlated with 11ß-HSD2 expression in males only, no significant correlations were found in the female only sample. CONCLUSION: These data indicate that the growth potential of a fetus is related to the 11ß-HSD2 expression in the placenta, and that 11ß-HSD2 expression is related to the trace metals status of the mother.

Clinical and genetic heterogeneity in chromosome 9p associated hereditary inclusion body myopathy: exclusion of GNE and three other candidate genes.

We have previously reported a new autosomal dominant inclusion body myopathy clinically resembling limb girdle muscular dystrophy, associated with Paget disease of bone in the majority and frontotemporal dementia in a third of individuals. The critical locus for this unique disorder now termed IBMPFD is 9 p21.1-p12, spans 5.5 Mb and contains the gene responsible for the recessive quadriceps-sparing inclusion body myopathy (IBM2). Mutation analysis of the GNE gene associated with IBM2 in affected individuals from four IBMPFD families did not identify any mutations, indicating that the two disorders are not allelic. Expression studies indicate that GNE has a tissue-specific splice pattern, with four splice variants. Mutation analysis in three other candidate genes (beta-tropomyosin, NDUFB6 and SMU1) did not identify any mutations.

Clinical heterogeneity in autosomal dominant optic atrophy in two 3q28-qter linked central Illinois families.

PURPOSE: To examine the clinical and genetic heterogeneity of autosomal dominant optic atrophy among two unrelated central Illinois families. METHODS: Forty-three individuals from two pedigrees had complete eye examinations. Linkage analysis was performed with microsatellite markers from the region 3q28-29. RESULTS: Visual acuity in 21 affected individuals ranged from 20/25 to 20/800. Vision loss was more severe in males than females (P = 0.02). Color vision testing revealed generalized dyschromatopsia. Both visual acuity and color vision deteriorated with age. Linkage was established to chromosome 3q28-29 (LODmax = 4.68 for D3S2305). CONCLUSION: Autosomal dominant optic atrophy linked to chromosome 3q28-29 shows intrafamilial phenotypic variation as well as sex-influenced severity in two Midwestern families.

Manifestations in four males with and an obligate carrier of the Lenz microphthalmia syndrome.

Lenz microphthalmia syndrome is a rare X-linked recessive condition first described by Lenz in 1955 and comprises of anophthalmia, microcephaly, mental retardation, external ear, digital, cardiac, skeletal, and urogenital anomalies. We present three brothers (ages 15 years, 9 years, and 18 months) and a maternal uncle (age 27 years) with congenital anophthalmia, delayed motor development, hypotonia, and moderate to severe mental retardation. They also have abnormally modeled ears, high-arched palate, pectus excavatum, finger and toe syndactyly, clinodactyly, fetal pads, scoliosis, cardiac, and renal abnormalities. An obligate carrier had abnormally modeled ears and syndactyly of the 2nd to 3rd toes bilaterally. Linkage and haplotype analysis in this family indicates that the gene is located in a 17.65-cM region on chromosome region Xq27-Xq28.

Anticipation in a unique family with Charcot-Marie-Tooth syndrome and deafness: delineation of the clinical features and review of the literature.

Charcot-Marie-Tooth disease (CMT) is a clinically and genetically heterogeneous group of polyneuropathies characterized by degeneration of peripheral nerves, resulting in distal muscle atrophy, sensory loss, and deformities of hands and feet. We have studied 34 individuals in a large 84-member four-generation central Illinois family with autosomal dominant Charcot-Marie-Tooth and deafness. Nerve conduction velocities are consistent with type 1 CMT. Audiological evaluation revealed both auditory neuropathy and cochlear involvement in affected individuals. There is increasing clinical severity and younger age of onset of CMT and deafness with each progressive generation, suggestive of anticipation (P < 0.05). The proband, a female diagnosed at birth with hypotonia, bilateral vocal cord palsy, swallowing incoordination, and hearing impairment, died at age 18 months. Another individual died at the age of 3 months from hypotonia later attributed to CMT. Genetic analysis indicated that affected individuals in this family do not have the common 1.4 Mb duplication associated with type 1A CMT; however, all affected individuals have a unique G to C transversion at position 248 in coding exon 3 of the peripheral myelin PMP22 gene located on chromosome 17p11.2-p12. This mutation is predicted to cause an Ala67Pro substitution in the second transmembrane domain of PMP22, consistent with the molecular cause of the CMT phenotype. However, it does not explain the cochlear component of the deafness, the clinical observation of anticipation, and other features in this family.

A Drosophila metallothionein promoter is inducible in mosquito cells.

Expression from a Drosophila metallothionein promoter (Mtn) was investigated in mosquito cells. Recombinant plasmids carrying a transcription unit comprised of the Escherichia coli beta-galactosidase gene (lacZ) fused to the metallothionein promoter were stably introduced into Aedes albopictus C6/36 cells. A low copy transformant containing approximately 60 copies of plasmid per cell, and a high copy transformant (1-2 x 10(4) copies/cell) were characterized. The expression of beta-galactosidase from the metallothionein promoter could be induced and controlled in this heterologous system, even when the copy number of introduced plasmid was several thousand.

Clinical and molecular studies in a unique family with autosomal dominant limb-girdle muscular dystrophy and Paget disease of bone.

PURPOSE: To characterize the clinical features and perform linkage analysis of candidate loci in a large Illinois family with autosomal dominant limb-girdle muscular dystrophy (LGMD) and Paget disease of bone (PDB). METHODS: The family includes 11 affected individuals (8 M, 3 F). Clinical, biochemical and radiologic evaluations were performed to delineate clinical features of the disorder. Linkage analysis with polymorphic markers was performed for previously identified LGMD, PDB and cardiomyopathy loci. RESULTS: Onset of PDB is early, at a mean age of 35 y, with classic distribution involving the spine, pelvis, and skull. Muscle weakness and atrophy is progressive with mildly elevated to normal creatine phosphokinase levels. Muscle biopsy in the oldest male revealed vacuolated fibers, however, in others revealed nonspecific myopathy. Affected individuals die from progressive muscle weakness, and respiratory and cardiac failure in their 40s-60s. Linkage analysis excluded autosomal dominant and recessive LGMD, PDB, and cardiomyopathy loci. CONCLUSION: Autosomal dominant LGMD associated with PDB is an unusual disorder. Linkage analysis indicates a unique locus in this family.

Stable transformation of a mosquito cell line results in extraordinarily high copy numbers of the plasmid.

Stable incorporation of high copy numbers (greater than 10,000 per cell) of a plasmid vector containing a gene conferring resistance to the antibiotic hygromycin was achieved in a cell line derived from the Aedes albopictus mosquito. Plasmid sequences were readily observed by ethidium bromide staining of cellular DNA after restriction endonuclease digestion and agarose gel electrophoresis. The plasmid was demonstrated by in situ hybridization to be present in large arrays integrated in metaphase chromosomes and in minute and double-minute replicating elements. In one subclone, approximately 60,000 copies of the plasmid were organized in a large array that resembles a chromosome, morphologically and in the segregation of its chromatids during anaphase. The original as well as modified versions of the plasmid were rescued by transformation of Escherichia coli using total cellular DNA. Southern blot analyses of recovered plasmids indicate the presence of mosquito-derived sequences.

Genetic heterogeneity in autosomal dominant essential tremor.

PURPOSE: To perform linkage analysis of candidate loci in a large Midwestern family with autosomal dominant essential tremor. METHODS: Thirty-eight members of a six-generation family were evaluated for essential tremor using consensus criteria. Linkage analysis was performed with microsatellite markers reported for three genetic loci associated with familial essential tremor. RESULTS: Patients exhibited a combination of postural and kinetic tremor involving primarily the arms and hands, with a mean age of onset of 31 years. Genetic studies excluded linkage to ETM1 and ETM2 loci, as well as a candidate locus for parkinsonism and postural tremor on chromosome 4p. CONCLUSION: Familial essential tremor is a common hereditary movement disorder demonstrating phenotypic variability and genetic heterogeneity.

A unique point mutation in the PMP22 gene is associated with Charcot-Marie-Tooth disease and deafness.

Charcot-Marie-Tooth disease (CMT) with deafness is clinically distinct among the genetically heterogeneous group of CMT disorders. Molecular studies in a large family with autosomal dominant CMT and deafness have not been reported. The present molecular study involves a family with progressive features of CMT and deafness, originally reported by Kousseff et al. Genetic analysis of 70 individuals (31 affected, 28 unaffected, and 11 spouses) revealed linkage to markers on chromosome 17p11.2-p12, with a maximum LOD score of 9.01 for marker D17S1357 at a recombination fraction of .03. Haplotype analysis placed the CMT-deafness locus between markers D17S839 and D17S122, a approximately 0.6-Mb interval. This critical region lies within the CMT type 1A duplication region and excludes MYO15, a gene coding an unconventional myosin that causes a form of autosomal recessive deafness called DFNB3. Affected individuals from this family do not have the common 1.5-Mb duplication of CMT type 1A. Direct sequencing of the candidate peripheral myelin protein 22 (PMP22) gene detected a unique G-->C transversion in the heterozygous state in all affected individuals, at position 248 in coding exon 3, predicted to result in an Ala67Pro substitution in the second transmembrane domain of PMP22.

Clinical delineation and localization to chromosome 9p13.3-p12 of a unique dominant disorder in four families: hereditary inclusion body myopathy, Paget disease of bone, and frontotemporal dementia.

Autosomal dominant myopathy, Paget disease of bone, and dementia constitute a unique disorder (MIM 605382). Here we describe the clinical, biochemical, radiological, and pathological characteristics of 49 affected (23 male, 26 female) individuals from four unrelated United States families. Among these affected individuals 90% have myopathy, 43% have Paget disease of bone, and 37% have premature frontotemporal dementia. EMG shows myopathic changes and muscle biopsy reveals nonspecific myopathic changes or blue-rimmed vacuoles. After candidate loci were excluded, a genome-wide screen in the large Illinois family showed linkage to chromosome 9 (maximum LOD score 3.64 with marker D9S301). Linkage analysis with a high density of chromosome 9 markers generated a maximum two-point LOD score of 9.29 for D9S1791, with a maximum multipoint LOD score of 12.24 between D9S304 and D9S1788. Subsequent evaluation of three additional families demonstrating similar clinical characteristics confirmed this locus, refined the critical region, and further delineated clinical features of this unique disorder. Hence, autosomal dominant inclusion body myopathy (HIBM), Paget disease of bone (PDB), and frontotemporal dementia (FTD) localizes to a 1.08-6.46 cM critical interval on 9p13.3-12 in the region of autosomal recessive IBM2.