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Enhanced susceptibility of mouse embryos heterozygous for oligosyndactyly (Os/+) to mitomycin C-induced skeletal abnormalities.

The mouse mutation, oligosyndactyly (Os), results in syndactyly, muscle anomalies, and deficiency of nephrons in heterozygous animals and early embryonic lethality in homozygotes. Since the homozygous lethality results from mitotic arrest with intact spindles at the time of implantation, we have hypothesized that the heterozygous manifestations may result from impairment of cell proliferation in regions with high proliferative rates. To test this hypothesis, Os/+ and +/+ mouse embryos at 6.5 days of gestation were exposed to mitomycin C (MMC), an agent that causes a high degree of embryonic cell death which is "compensated" for by a period of rapid cell proliferation. 17.9% of MMC-treated +/+ fetuses had fused vertebrae, a significant increase over untreated fetuses, and this frequency was further increased to 33.6% in MMC-treated Os/+ fetuses. Saline treated Os/+ and +/+ fetuses showed the same low rate (0-3%) of vertebral fusion. These results indicate that Os/+ embryos have an increased sensitivity to the vertebral fusion-inducing effect of MMC at 6.5 days of gestation, a finding compatible with the hypothesis that rapid cell proliferation may be impaired in Os/+ embryos and fetuses.

Animals↗

In vivo evidence that BMP signaling is necessary for apoptosis in the mouse limb.

To determine the role of Bone morphogenetic protein (BMP) signaling in murine limb development in vivo, the keratin 14 promoter was used to drive expression of the BMP antagonist Noggin in transgenic mice. Phosphorylation and nuclear translocation of Smad1/5 were dramatically reduced in limbs of the transgenic animals, confirming the inhibition of BMP signaling. These mice developed extensive limb soft tissue syndactyly and postaxial polydactyly. Apoptosis in the developing limb necrotic zones was reduced with incomplete regression of the interdigital tissue. The postaxial extra digit is also consistent with a role for BMPs in regulating apoptosis. Furthermore, there was persistent expression of Fgf8, suggesting a delay in the regression of the AER. However, Msx1 and Msx2 expression was unchanged in these transgenic mice, implying that induction of these genes is not essential for mediating BMP-induced interdigital apoptosis in mice. These abnormalities were rescued by coexpressing BMP4 under the same promoter in double transgenic mice, suggesting that the limb abnormalities are a direct effect of inhibiting BMP signaling.

Animals↗

Mutations of the mouse Twist and sy (fibrillin 2) genes induced by chemical mutagenesis of ES cells.

A prior phenotype-based screen of mice derived from ethylmethanesulfonate-mutagenized embryonic stem cells yielded two mouse limb defect mutants. Animals heterozygous for the polydactyly ems (Pde) mutation display preaxial polydactyly of the hindlimbs, and homozygous syndactyly ems (sne) animals are characterized by a fusion of the middle digits of their hindlimbs and sometimes forelimbs. We now report that Pde is a new allele of the basic helix-loop-helix protein gene Twist. Sequencing the full-length cDNA and several hundred basepairs of genomic DNA upstream of the coding region failed to reveal a mutation, suggesting that the lesion may be in a regulatory element of the gene. sne is a new fused phalanges (fp) allele of the shaker-with-syndactylism deletion complex (sy), and we show that the genomic lesion is a small deletion removing an entire exon, coincident with the insertion of the 3' end of a LINE element belonging to the TF subfamily.

Alleles↗

Oculodental digital dysplasia: neuroimaging in a kindred.

Oculodental digital dysplasia (ODDD) is an uncommon inherited disorder with characteristic facial abnormalities, defects in dentition and syndactyly; previous reports have described neurologic dysfunction. We present neuroimaging features of a mother and daughter with ODDD; despite only the mother having neurologic dysfunction, the MRI findings in both are strikingly similar.

Adolescent↗

Fraser-cryptophthalmos syndrome.

Fraser or Cryptophthalmos syndrome is a variable syndrome to the extent that cryptophthalmos might not be present in all cases. However, the main features are a "hidden eye", other craniofacial abnormalities, renal abnormalities, syndactyly and abnormal genitalia. It may be classified as isolated cryptophthalmos or cryptophthalmos sequence and cryptophthalmos syndrome. The cryptophthalmos syndrome has an autosomal recessive mode of inheritance. Isolated cryptophthalmos has been reported as an autosomal dominant trait. Prenatal diagnosis is possible using ultrasonography and fetoscopy. We report three cases of cryptophthalmos. One with renal agenesis had cryptophthalmos syndrome and the other two had isolated cryptophthalmos or cryptophthalmos sequence.

Abnormalities, Multiple↗

The duplicated longitudinal epiphysis or "kissing delta phalanx": evolution and variation in three different disorders.

BACKGROUND: The delta phalanx, also known as the delta bone, or longitudinal epiphyseal bracket (LEB), has been described in a variety of syndromes and dysplasias. However, the "kissing delta phalanx" is not as well recognized in the literature; it consists of a duplicated longitudinal bracketed epiphysis, or a complex of two adjacent delta bones, with opposing convex portions facing each other. Magnetic resonance imaging of the kissing delta phalanx has not been previously described. OBJECTIVE: To describe the evolution, variation and associated osseous anomalies of the kissing delta phalanx in three patients with distinct distal limb malformations using both plain films and magnetic resonance imaging. RESULTS: Patient 1 had Rubinstein-Taybi syndrome and, in addition to a kissing delta phalanx in both feet, had corresponding delta metatarsals (MT1). Patient 2 had Cenani-Lenz syndactyly with distinct variation of the kissing delta phalanx in each hand. He had a disorganized appearance to the phalanges, metacarpal fusions and carpal coalitions. Patient 3 had an isolated oligosyndactyly of the left hand with metacarpal fusions and carpal coalitions. All three patients were followed over time. We describe two types of kissing delta phalanges: separated (without fusion of the corresponding epiphyseal brackets) and nonseparated (with fusion of the corresponding epiphyseal brackets). Both types can be seen in the same patient and are a reflection of the relative degree of segmentation of the two delta bones. CONCLUSION: The appearance of this rare osseous abnormality changes with time and can be found in a limited number of uncommon disorders. It can also be found in association with other osseous anomalies of the distal extremities; therefore magnetic resonance imaging early in life can greatly assist in surgical planning. Recognition of the kissing delta phalanx may be an important radiological clue to diagnosis of these rare disorders.

Child, Preschool↗

Genetics analysis of mouse mutations Abnormal feet and tail and rough coat, which cause developmental abnormalities and alopecia.

Mutations in the mouse Brachyury (T) gene are characterized by a dominant reduction of tail length and recessive lethality. Two quantitative trait loci, Brachyury-modifier 1 and 2 (Brm1 and Brm2) are defined by alleles that enhance the short-tail Brachyury phenotype. Here we report on a genetic analysis of a visible dominant mutation Abnormal feet and tail (Aft) located in the vicinity of Brm1. Affected animals display kinky tails and syndactyly in the hindlimbs, both likely resulting from a defect in apoptosis. We observed an unusual genetic incompatibility between Aft and certain genetic backgrounds. We show that Aft and T are likely to interact genetically, since some double heterozygotes are tailless. In addition to the tail and hindlimb phenotypes, Aft-bearing mutants display characteristic late-onset skin lesions. We therefore tested for allelism between Aft and a closely linked recessive mutation rough coat (rc) and found that these two mutations are likely nonallelic. Our results provide a valuable resource for the study of mammalian skin development and contribute to the genetic analysis of Brachyury function.

Abnormalities, Multiple↗

Ft1, a novel gene related to ubiquitin-conjugating enzymes, is deleted in the Fused toes mouse mutation.

The dominant mouse mutation Fused toes is characterized by partial syndactyly of the limbs and thymic hyperplasia. Both morphological abnormalities were shown to be related to impaired regulation of programmed cell death. Ft/Ft embryos die in midgestation showing severe malformations of fore- and midbrain as well as randomized situs. In Ft mice a large chromosomal deletion (about 300 kb) occurred after insertional mutagenesis. In this report we describe the identification of the first gene that has been mutated by Fused toes. The expression of the novel gene Ft1 is reduced in Ft/+ mice and completely absent in Ft/Ft embryos. Analysis of the Ft1 cDNA revealed an open reading frame that could code for a 32-kDa protein with similarities to ubiquitin-conjugating enzymes. Ft1 transcripts with alternative 5' UTR sequences as well as differential usage of polyadenylation sites were found. Interestingly, the 3' parts of the longest Ft1 transcripts are identical to the reverse complement of the 3'-most sequences of the Rb-related p130 gene. Both genes are transcribed in opposite directions and overlap in their 3' UTRs. Despite the close linkage, p130 expression appeared not to be affected by the Ft mutation. In wild type mice, Ft1 expression levels were found to be high in brain, kidney, and testes and detectable in all other adult organs and throughout embryonic development. Finally, we show that Ft1 is conserved among mammals and identify the human homolog.

Abnormalities, Multiple↗

Urogenital sinus, rectovaginal fistula, and an anterior stenosed anus--another cloacal variant.

The persistent cloaca is one of the most complex and challenging developmental malformations. It is a rare anomaly occurring only in the female newborn and is represented by the association of urogenital sinus with an anorectal malformation (ARM). Each case is probably unique. We report here one such case of cloaca with the VATER association-tracheoesophageal fistula (TOF) with a urogenital sinus, rectovaginal fistula, and an anteposed stenosed anus, along with preaxial syndactyly of the right hand. The spine, renal, and cardiac systems were normal. Interim management was directed towards repair of the TOF and a right transverse defunctioning colostomy. Despite thorough radioendoscopic preoperative investigations, the complexity of the cloacal anomaly was not delineated until surgery. This case is a rather rare combination of an intermediate form of the cloacal-ARM spectrum. Such patients present with many diagnostic and therapeutic problems. Interval surgery should be directed towards decompression of the affected organ systems, and definitive surgery must be carefully planned and, whenever possible, done in a single stage with simultaneous multisystem repair to correct all significant malformations related to the cloacal complex.

Abnormalities, Multiple↗

Changes in expression of the lysosomal membrane glycoprotein, LAMP-1 in interdigital regions during embryonic mouse limb development, in vivo and in vitro.

Syndactyly, a failure of the digits to separate into individual units, affects about 8 to 9 per 1000 newborns and results from an aberration of the normal development of the interdigital tissues. Limb digit separation is the result of programmed cell death (apoptosis). Lysosomes play a role in the process of cell self-destruction. Our experiment was designed to test the hypothesis that the intensity of interdigital lysosomes increases during the separation of digits in vivo and in vitro. The primary mouse monoclonal antibody, 1D4B, detects the presence of lysosomes by identifying the LAMP-1 glycoprotein on the lysosome cell membrane. In our experiment this antibody immunodetected interdigital lysosome proteins in serial sections of limbs from Swiss-Webster mouse embryos, gestational ages E12.5 through E15, key developmental stages for digit separation. Digit separation was associated with an increase in intensity of lysosomal protein staining. In E12.5 limbs, the presence of lysosomes was enriched in the distal aspect of the interdigital tissue. However, the number of lysosomes markedly increased in the E13 and E14 limbs, including the entire length and width of the interdigital tissue in the E14 limbs. This lysosomal protein presence in E14 limbs was significant compared to E12.5, E13, and E15 limbs. By day 12.5, the mouse embryo limb is committed to digit separation. Addition of retinoic acid to the culture medium of limbs earlier in development, such as E12, results in induction of the process of digit separation. Cultured E12 limbs that did not receive an addition of retinoic acid, did not show digit separation. We conclude that in the limb development process, the enrichment in interdigit LAMP-1 proteins, may indicate a relationship between lysosomes, apoptosis, and digit separation. We also conclude that retinoic acid has an important role in digit separation in vivo, as shown in limb development, and demonstrated through the addition of retinoic acid to media of cultured tissues.

Animals↗

Hereditary cataracts in deer mice (Peromyscus maniculatus).

A new type of hereditary cataract was predicted in the deer mouse (Peromyscus maniculatus) by the presence of syndactyly of the hind feet. Early morphologic changes were found in the equatorial cells that differentiated into new lens fibers. Later swelling at the anterior and posterior poles of these cells produced lens opacities. Anterior and posterior subcapsular cataracts progressed to a hypermature shrunken lens.

Animals↗

Cryptophthalmos syndrome with bilateral renal agenesis.

We conducted a postmortem study of an infant with the abortive form of the cryptophthalmos syndrome. He had syndactyly and anal atresia and also showed features of Potter's (renal nonfunction) syndrome, including bilateral renal agenesis, pulmonary hypoplasia, and the typical facies. Histopathologic examination of both globes disclosed that the superior eyelid folds were partially replaced by skin that fused with the superior third of each cornea; there were also anomalies of the superior canaliculi and scarring of the corneas. We found no specific abnormality of the intraocular contents.

Abnormalities, Multiple↗

Extended use of the Mustardé dancing man procedure.

Webs other than epicanthal folds can be corrected by the Mustardé "dancing man" procedure. A series of 20 patients is presented in whom this method has been used to correct either minor degrees of congenital syndactyly or burn scar contractures in fingers.

Adolescent↗

Oligosyndactyly: a lethal mutation in the mouse that results in mitotic arrest very early in development.

The mutation, oligosyndactyly, results in syndactyly, muscle anomalies, and diabetes insipidus in heterozygous mice. When homozygous, the mutation is lethal early in development. Although homozygous embryos are able to form blastocyst outgrowths (the in vitro equivalent to implantation), cells begin to accumulate in mitosis as early as the blastocyst stage. Even though the cytologic appearance is that of mitotic cells treated with a microtubule inhibitor such as colcemid, the homozygous embryos do, in fact, have normal appearing mitotic spindles. These results define the Os mutation as one which, in the homozygous state, prevents the movement of chromosomes from the metaphase plate. It is the first mammalian developmental mutation to be so defined and is unique among all mitotic arrest mutations thus far described in higher eucaryotes.

Animals↗

Fraser syndrome: a case report and review of the otolaryngologic manifestations.

Fraser syndrome is a rare autosomal recessive disorder whose major manifestations are cryptophthalmos, syndactyly and genital abnormalities. These patients also frequently have malformations of the ears, nose and/or larynx. The diagnosis is usually made at birth from the obvious malformations, although occasionally made on prenatal ultrasound. Treatment is dependent on which malformations are present and genetic counseling is indicated. Prognosis is dependent on the severity of renal and laryngeal malformations.

Coloboma↗

The position of symbrachydactyly in the classification of congenital hand anomalies.

The clinical features of 53 cases of intercalated hypoplasia and 113 cases of distal aplasia are reviewed and compared with each other and with 129 cases of syndactyly. Tri-, di- and mono-phalangeal symbrachydactyly, and adactyly with nubbin digits are consecutive anomalies. Transverse deficiency may result if the mesenchyme is damaged severely, and if damage is mild and formation has continued, intercalated transverse deficiency may occur. Webbing in symbrachydactyly may result from failure of the apical ectodermal ridge under the influence of damaged mesenchyme.

Female↗

Web space reconstruction with a M-V flap.

An operative technique for the construction of a supple and broad commissure in syndactyly and web contracture release is introduced. The technique is based on a M-V flap framework. Sixty-three flaps were done in 33 patients who were followed-up for an average of 19 months. Excellent results were obtained in 90% of the cases. There were no neurologic or vascular complications in any of these cases. The versatility of this method has allowed its use in the majority of our cases that necessitated web release or web space reconstruction.

Adolescent↗