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At least 847 records · Page 47Linked to original sources
PubMed1994

Cloning of MITF, the human homolog of the mouse microphthalmia gene and assignment to chromosome 3p14.1-p12.3.

The mouse microphthalmia (mi) gene encodes a basic-helix-loop-helix-zipper protein whose mutations may lead to loss of pigmentation in the eye, inner ear and skin, and to reduced eye size and early onset deafness. Mice with mutations at mi serve as models for human pigment disturbances in skin and eye that may be combined with sensorineural deafness. We have now obtained cDNA and genomic clones of the human homolog of mouse mi, identified a restriction fragment length polymorphism in the gene, and mapped the gene by somatic cell hybrid and fluorescence in situ hybridization techniques to a region of human chromosome 3 that shows a disrupted syntenic conservation with the region on mouse chromosome 6 to which mi maps. These studies will help to verify if any of the hereditary pigment disturbances in humans are due to mutations in this gene.

Amino Acid Sequence↗
PubMed1994

A YAC-based binning strategy facilitating the rapid assembly of cosmid contigs: 1.6 Mb of overlapping cosmids in Xp22.

We have applied a yeast artificial chromosome (YAC)-based cosmid isolation and binning strategy to convert a YAC contig in Xp22 into 1.6 Mb of overlapping cosmids. This strategy is based on the screening of a high-density arrayed X chromosome-specific cosmid library with large YAC-derived restriction fragments and entire YAC probes. Cosmids selected in this way were gridded on dot blots and further mapped into bins defined by the overlap intervals of the YACs and YAC fragments. This rapid binning of cosmids simplified the subsequent assembly of cosmid contigs by restriction fingerprint hybridization. In total, we identified 139 cosmids spanning the entire 1.6 Mb region with a minimal overlap set of 53 clones. These cosmids were assigned to 17 bins and 9 contigs. One of the contigs is 665 kb in length and is one of the largest uninterrupted cosmid contigs in humans reported to date. The gaps between the contigs are minor and, together, they represent less than 7% of the region covered. Two previously identified genes are contained in these cosmids, the gene for amelogenin (AMG) and the recently isolated putative chloride channel gene CICN4. In addition, two disease loci have been mapped to this region: X-linked ocular albinism type 1 (OA1) and the microphthalmia with linear skin defects (MLS) syndrome. The assembly of the cosmid maps allowed us to determine the size of the deletion intervals for these two loci, which were estimated to be 110 kb for OA1 and 570 kb for MLS.(ABSTRACT TRUNCATED AT 250 WORDS)

Albinism, Ocular↗
PubMed2000

Functional analysis of ARHGAP6, a novel GTPase-activating protein for RhoA.

Microphthalmia with linear skin defects (MLS) is an X-linked dominant, male-lethal syndrome characterized by microphthalmia, aplastic skin and agenesis of the corpus callosum, and is caused by the deletion of a 500 kb critical region in Xp22.3. Our laboratory isolated a novel rho GTPase-activating protein (rhoGAP) gene named ARHGAP6 from the MLS region. ARHGAP6 contains 14 exons encoding a 974 amino acid protein with three putative SH3-binding domains. Because exons 2-14 are deleted in all MLS patients, we hypothesized that ARHGAP6 may be responsible for some of the phenotypic features of MLS. We pursued two approaches to study the function of ARHGAP6 and its role in the pathogenesis of MLS: gene targeting of the rhoGAP domain in mouse embryonic stem cells and in vitro expression studies. Surprisingly, loss of the rhoGAP function of Arhgap6 does not cause any detectable phenotypic or behavioral abnormalities in the mutant mice. Transfected mammalian cells expressing ARHGAP6 lose their actin stress fibers, retract from the growth surface and extend thin, branching processes resembling filopodia. The ARHGAP6 protein co-localizes with actin filaments through an N-terminal domain and recruits F-actin into the growing processes. Mutation of a conserved arginine residue in the rhoGAP domain prevents the loss of stress fibers but has little effect on process outgrowth. These results suggest that ARHGAP6 has two independent functions: one as a GAP with specificity for RhoA and the other as a cytoskeletal protein that promotes actin remodeling.

Actins↗
PubMed2003

Targeted disruption of exons 1 to 6 of the Fanconi Anemia group A gene leads to growth retardation, strain-specific microphthalmia, meiotic defects and primordial germ cell hypoplasia.

Fanconi Anemia (FA) is an autosomal recessive disorder characterized by cellular hypersensitivity to DNA cross-linking agents. Recent studies suggest that FA proteins share a common pathway with BRCA proteins. To study the in vivo role of the FA group A gene (Fanca), gene-targeting techniques were used to generate Fanca(tm1Hsc) mice in which Fanca exons 1-6 were replaced by a beta-galactosidase reporter construct. Fanca(tm1.1Hsc) mice were generated by Cre-mediated removal of the neomycin cassette in Fanca(tm1Hsc) mice. Fanca(tm1.1Hsc) homozygotes display FA-like phenotypes including growth retardation, microphthalmia and craniofacial malformations that are not found in other Fanca mouse models, and the genetic background affects manifestation of certain phenotypes. Both male and female mice homozygous for Fanca mutation exhibit hypogonadism, and homozygous females demonstrate premature reproductive senescence and an increased incidence of ovarian cysts. We showed that fertility defects in Fanca(tm1.1Hsc) homozygotes might be related to a diminished population of primordial germ cells (PGCs) during migration into the gonadal ridges. We also found a high level of Fanca expression in pachytene spermatocytes. Fanca(tm1Hsc) homozygous males exhibited an elevated frequency of mispaired meiotic chromosomes and increased apoptosis in germ cells, implicating a role for Fanca in meiotic recombination. However, the localization of Rad51, Brca1, Fancd2 and Mlh1 appeared normal on Fanca(tm1Hsc) homozygous meiotic chromosomes. Taken together, our results suggest that the FA pathway plays a role in the maintenance of reproductive germ cells and in meiotic recombination.

Animals↗
PubMed1996

The descriptive epidemiology of anophthalmia and microphthalmia.

BACKGROUND: Anophthalmia and microphthalmia are serious eye malformations which recently have been associated with exposure to Benomyl. Data on these malformations are scarce in the literature and reported prevalences at birth vary strongly. METHODS: Data from three large registers of congenital malformations were analysed and comprised 849 malformed infants based on close to 5.7 million births. RESULTS: This is the largest available epidemiological study on anophthalmia and microphthalmia. The prevalence at birth was 1.50 per 10,000, varying between 0.92 and 2.29 between registers but no varying significantly between races in the California register. The variation in rates was mainly due to different inclusion of chromosomally abnormal infants (mainly trisomy 13) and of infants with microphthalmia occurring with major non-eye malformations. On the other hand, rates of anophthalmia and isolated microphthalmia were similar. Other major non-eye malformations were found in 73% of infants without a known chromosome anomaly. The malformation was bilateral in 53-60% of infants except when microphthalmia existed without any other malformations when only 27% were bilateral. Sex distribution was normal, there was a slight excess of twins, and an increased risk at high maternal age. CONCLUSIONS: In analytical studies searching for the cause of these malformations, it may be useful to restrict the analysis to infants with anophthalmia or isolated microphthalmia as the recording of such cases seems to be more reliable than of microphthalmia occurring with other malformations. The conclusions presented in the literature on the possible effect of Benomyl are partly based on data with apparent very incomplete ascertainment.

Abnormalities, Multiple↗
PubMed2005

Partial rescue of B cells in microphthalmic osteopetrotic marrow by loss of response to type I IFNs.

The microphthalmic (mi) mouse exhibits deficiencies in the development of osteoclasts, melanocytes, mast cells and marrow B cells. Previously, we demonstrated that the marrow of such mice over-express receptor activator of nuclear factor kappaB (RANK) ligand (RANKL). RANKL has been shown to induce the production of IFN-beta, a type I IFN. Additionally, maturing B cells have been shown to undergo apoptosis in response to type I IFNs including IFN-beta during differentiation. We hypothesized that the loss of B cells in the marrow of mi mice was due to the over-expression of IFN-beta as a result of heightened RANK-RANKL signaling. Creating a mouse with the mi genotype that was non-responsive to IFN-beta (lacking the type I IFNR) allowed us to test this hypothesis. These mice demonstrated an elevated number of marrow B cells and marrow precursor cells compared with mi animals possessing the type I IFNR. Intriguingly, type I IFNR-deficient wild-type animals also demonstrated an increased number of precursor cells in the marrow, but not an expansion of B220-positive pre-B cells, compared with wild type, suggesting that modulation of type I IFN responses directly controls the development of marrow constituents.

Animals↗
PubMed2001

Participation of a preschooler with visual impairments on the playground: effects of musical adaptations and staff development.

The purpose of this study was to evaluate the adaptations of a playground, and subsequently staff development, on the participation of a 3-year-old boy with congenital blindness. A single-subject design with three conditions (baseline, adaptations of the playground, and staff development) was used. The playground adaptation involved adding musical stations in strategic locations on the playground and connecting them with a "path" that provided auditory feedback. The staff training involved the music therapist providing individualized instruction to the staff who supervised the child. The child's participation was measured in terms of social interaction with peers or adults, play and engagement with materials, movement on the playground, and stereotypic behaviors. The playground adaptation resulted in no changes in the child's social interactions with peers or adults, increases in engagement, no change in movement on the playground, and a decrease in stereotypic responses. Staff training resulted in increased but variable interactions with adults and peers, in additional increases in engagement, less movement, and similar levels of stereotypic behavior. The findings suggest that musical adaptations of physical environments may he helpful but not sufficient for promoting desired outcomes.

Blindness↗
PubMedDate not supplied

Congenic strains of RCS rats with inherited retinal dystrophy.

Two congenic strains of RCS rats, RCS-p/+ and RCS-c, have been developed that differ from the parental strain at genetic loci affecting pigmentation. Inbred RCS rats are pink-eyed, while RCS-p/+ rats produce segregating litters of pink-eyed (p/p) and black-eyed (p/+) offspring, and RCS-c rats are albinos. All the strains are homozygous for the mutant form of the retinal dystrophy gene. The black eye pigment in RCS-p/+ rats slows the progression of the retinal degeneration by about 10 days in the posterior retina and by about 30-35 days in the peripheral retina in the superior half of the eye. No slowing of the disease occurs in the inferior half of the eye along the vertical meridian. All the strains are similar in body weight and litter size, and show a low incidence of cataract and microphthalmia.

Albinism↗
PubMedDate not supplied

The vit gene maps to the mi (microphthalmia) locus of the laboratory mouse.

The murine model for human vitiligo (the vit/vit mouse) develops progressive depigmentation of the pelage, skin, and eyes. The vit gene is inherited as an autosomal recessive. We have used classical breeding and isozyme marker analysis to map this vit gene that produces a vitiligo-like condition in the mouse. Crossbreeding the C57BL/6J-vit/vit mice with C57BL/6J mice carrying the Miwh and/or miws alleles at the microphthalmia locus resulted in mutant phenotypes, demonstrating absence of complementation. When vit is heterozygous with the Miwh allele, a "blotched" pigment pattern results. When it is heterozygous with the miws allele, a novel expression of the vitiliginous phenotype results. Further mating analysis of these crossbred populations demonstrates allelic inheritance between vit and the alleles at the microphthalmia locus. Other breeding studies using alleles at the agouti, belted, brown, dominant spotting, extension, mahogany, patch, and piebald loci did not demonstrate pigmentation explainable by allelic inheritance with the vit gene. Also, vit was tested for linkage with isozyme markers located on chromosomes 1, 4, 5, 7, 9, and 11, and results were negative. Therefore, the vit (vitiligo) gene of the laboratory mouse has been mapped to the mi (microphthalmia) locus on chromosome 6. The gene properly should be designated as mivit.

Alleles↗
PubMed1998

Unilateral dermis-fat graft implantation in the pediatric orbit.

The purpose of this study was to evaluate the role of the dermis-fat graft (DFG) as an orbital implant in the pediatric age group. A retrospective study was made of a series of 16 patients who had undergone unilateral orbital implantation of a DFG. The ages of the patients at the time of surgery ranged from 2 months to 17 years, with followup ranging from 2 to 15 years. Growth of the graft was clinically apparent in the younger children. Increasing proptosis required surgical debulking of the graft in six of eight children who were 4 years old or younger at the time of DFG implantation. None of the eight children who were 9 years or older at the time of DFG implantation required surgical debulking. Indeed, five of the older patients demonstrated some degree of graft atrophy. Dermis-fat grafts placed in the orbits of young children appear to grow after implantation. This growth of the implant may help stimulate orbital growth, potentially leading to more symmetry between the involved and uninvolved sides.

Adipose Tissue↗
PubMed2002

Congenital upper eyelid coloboma and cryptophthalmos.

PURPOSE: To discuss the relation between congenital upper eyelid coloboma and cryptophthalmos and to present a new grading for both conditions. METHODS: Observational case series study. Twenty-six children (age range, one day after birth to 15 years old) were included in the study: 19 with upper eyelid coloboma, 4 with classic cryptophthalmos, and 3 with both eyelid coloboma and cryptophthalmos. RESULTS: Of the 19 cases of upper eyelid coloboma, 5 occurred in isolation, 11 were associated with facial deformities, and 3 were part of a first arch syndrome (according to the Mustardé classification). All cases of classic cryptophthalmos were sporadic and nonsyndromic. All patients with coloboma with facial deformities, cryptophthalmos, and both eyelid coloboma and cryptophthalmos had similar associated facial abnormalities. CONCLUSION: Upper eyelid colobomas with facial deformities and cryptophthalmos can be considered as one anomaly. A new grading for this anomaly has been suggested. Grade 1: Coloboma without cryptophthalmos. Grade 2: Coloboma with abortive cryptophthalmos. Grade 3: Coloboma with complete cryptophthalmos. Grade 4: Classic cryptophthalmos (absence of all eyelid structures and the eye is completely covered with skin). Grade 5: Severe cryptophthalmos (with severe deformity of the nose and ectropion of the upper lip).

Adolescent↗
PubMed1979

Classification of oblique facial clefts with microphthalmia.

We believe the Tessier classification system facilitates the description of complicated facial clefts, and we describe its use in 4 cases--all of whom had variations of a Tessier-3 cleft. Microphthalmia is associated with the Tessier-3 cleft. Computerized axial tomography may be helpful in differentiating an extreme microphthalmia from a true anophthalmia, and in detecting bony clefts not seen on roentgenographic studies. Facial tomograms show that abnormalities of the medial wall of the orbit in the Tessier-3 cleft vary from actual clefts to widening of the ethmoid. In our experience (with 4 patients) mental retardation does not necessarily occur in patients with the Tessier-3 cleft and extreme microphthalmia. Abnormalities of the nasolacrimal apparatus may be the most constant finding in patients with the Tessier-3 cleft. Children with the Tessier-3 cleft should be identified early for purposes of determining the proper treatment and valid genetic counseling.

Anophthalmos↗
PubMed1995

Complete nasal agenesis with bilateral microphthalmia and unilateral duplication of the thumb.

Complete nasal aplasia is an extremely rare clinical entity and most infants are stillborn when this is associated with holoprosencephaly. A viable 3-year-old infant born with frontonasal arrest without holoprosencephaly is presented. The child's main complaint was lack of a nasal airway, which made eating extremely difficult. A method for craniofacial reconstruction of the nasopharynx is presented.

Abnormalities, Multiple↗
PubMed1988

Nanophthalmic uveal effusion.

A nanophthalmic patient with hypermetropia, shortened anterior-posterior axial length, and thickened choroid presented with a choroidal detachment and nonrhegmatogenous retinal detachment (NRRD). He underwent partial thickness, 5 x 7 mm, sclerectomies and 1-2 mm central sclerostomies 9.5 mm posterior to the limbus, specifically avoiding vortex veins. Complete resolution of the retinal and choroidal detachments occurred in spite of postoperative ultrasonograms demonstrating residual choroidal-scleral thickening. The effectiveness of this technique in our patient, in light of recent studies demonstrating histochemical and microscopic abnormalities in nanophthalmic sclera, suggests impairment of trans-scleral protein transport as the primary pathophysiologic mechanism in nanophthalmic uveal effusion.

Exudates and Transudates↗