Specification and morphogenesis of the zebrafish larval head skeleton.
(49/620)
Forward genetic analyses can reveal important developmental regulatory genes and how they function to pattern morphology. This is because a mutated gene can produce a novel, sometimes beautiful, phenotype that, like the normal phenotype, immediately seems worth understanding. Generally the loss-of-function mutant phenotype is simplified from the wild-type one, and often the nature of the pattern simplification allows one to deduce how the wild-type gene contributes to patterning the normal, more complex, morphology. This truism seems no less valid for the vertebrate head skeleton than for other and simpler cases of patterning in multicellular plants and animals. To show this, we review selected zebrafish craniofacial mutants. "Midline group" mutations, in genes functioning in one of at least three signal transduction pathways, lead to neurocranial pattern truncations that are primarily along the mediolateral axis. Mutation of lazarus/pbx4, encoding a hox gene partner, and mutation of valentino/kreisler, a hox gene regulator, produce anterior-posterior axis disruptions of pharyngeal cartilages. Dorsoventral axis patterning of the same cartilages is disrupted in sucker/endothelin-1 mutants. We infer that different signal transduction pathways pattern cartilage development along these three separate axes. Patterning of at least the anterior-posterior and dorsoventral axes have been broadly conserved, e.g., reduced Endothelin-1 signaling similarly perturbs cartilage specification in chick, mouse, and zebrafish. We hypothesize that Endothelin-1 also is an upstream organizer of the patterns of cellular interactions during cartilage morphogenesis. (+info)
Analysis of the cat eye syndrome critical region in humans and the region of conserved synteny in mice: a search for candidate genes at or near the human chromosome 22 pericentromere.
(50/620)
We have sequenced a 1.1-Mb region of human chromosome 22q containing the dosage-sensitive gene(s) responsible for cat eye syndrome (CES) as well as the 450-kb homologous region on mouse chromosome 6. Fourteen putative genes were identified within or adjacent to the human CES critical region (CESCR), including three known genes (IL-17R, ATP6E, and BID) and nine novel genes, based on EST identity. Two putative genes (CECR3 and CECR9) were identified, in the absence of EST hits, by comparing segments of human and mouse genomic sequence around two solitary amplified exons, thus showing the utility of comparative genomic sequence analysis in identifying transcripts. Of the 14 genes, 10 were confirmed to be present in the mouse genomic sequence in the same order and orientation as in human. Absent from the mouse region of conserved synteny are CECR1, a promising CES candidate gene from the center of the contig, neighboring CECR4, and CECR7 and CECR8, which are located in the gene-poor proximal 400 kb of the contig. This latter proximal region, located approximately 1 Mb from the centromere, shows abundant duplicated gene fragments typical of pericentromeric DNA. The margin of this region also delineates the boundary of conserved synteny between the CESCR and mouse chromosome 6. Because the proximal CESCR appears abundant in duplicated segments and, therefore, is likely to be gene poor, we consider the putative genes identified in the distal CESCR to represent the majority of candidate genes for involvement in CES. (+info)
Localisation of a gene for an autosomal recessive syndrome of macrocephaly, multiple epiphyseal dysplasia, and distinctive facies to chromosome 15q26.
(51/620)
BACKGROUND: We have previously described an autosomal recessive syndrome of macrocephaly, multiple epiphyseal dysplasia (MED), and distinctive facies in a large, extended Omani family. The MED observed seems to be part of a larger malformation syndrome, since both craniofacial and central nervous system changes were present in the family. We performed a whole genome scan in this family in order to identify the gene locus for this malformation syndrome. METHODS AND RESULTS: Using homozygosity mapping, we show linkage to the telomeric region of the long arm of chromosome 15. The position of both the disease gene and the principal glycoprotein, chondroitin sulphate proteoglycan (aggrecan, AGC1) on chromosome 15q26, suggested that the aggrecan gene is a candidate for the disease in this family. However, three of the four affected children were heterozygous for a polymorphism at position 831 of the coding sequence of AGC1, providing strong evidence against its involvement. CONCLUSION: We have identified a gene locus for a recessive syndrome of macrocephaly, MED, and distinctive facies in a large Omani family. Aggrecan located on chromosome 15q26, within the critical region determined for this syndrome in this family, was excluded as a candidate gene. (+info)
Linkage of otopalatodigital syndrome type 2 (OPD2) to distal Xq28: evidence for allelism with OPD1.
(52/620)
Otopalatodigital syndrome type 1 (OPD1) is an X-linked semidominant condition characterized by malformations of the skeleton, auditory apparatus, and palate. Previous studies have established linkage to a 16-cM region of Xq27-q28. A proposed allelic variant of OPD1, termed "OPD2," is associated with a more severe, frequently lethal phenotype with visceral and brain anomalies in addition to skeletal, auditory, and palatal defects. We report linkage of the OPD2 phenotype to a 2-cM region of distal Xq28 in a Maori kindred, with a maximum multipoint LOD score of 3.31 between the markers DXS1073 and DXS1108. This provides support for allelism between OPD1 and OPD2 and reduces the size of the disease interval to 1.8-2.1 Mb. We also demonstrate that female carriers of this disorder exhibit skewed inactivation that segregates with the high-risk haplotype and may be inversely related to the severity with which they manifest features of the disorder. (+info)
A longitudinal evaluation of craniofacial growth in a patient with Kabuki make-up syndrome: a case report.
(53/620)
The purpose of this investigation was to evaluate the craniofacial growth of a patient diagnosed with Kabuki make-up syndrome (KMS). Craniofacial growth was assessed by analysing lateral cephalometric radiographs with an interval of 12-15 months. They were taken from 6 years 9 months to 14 years 2 months. Angular and linear measurement analyses of the craniofacial complex showed a hypoplastic maxilla and a constricted maxillary basal arch width. The mandibular size was relatively large and had started to increase from 13 years 4 months. This resulted in a prognathic face caused by forward growth of the mandible and insufficient growth of the maxilla. The skeletal pattern was Class III. Open bite morphology with a steep mandibular plane (SN-MP), a relatively short ramus, and a large gonial angle were also observed. In this subject, the facial dysmorphism found in the maxilla and mandible may have been influenced by several factors. Connective tissue disorder, macroglossia, lower tongue posture, and tongue thrust swallowing have been identified as possible aetiological factors that may determine dysmorphism in the craniofacial complex in this KMS patient. (+info)
Voltage-gated calcium channel gamma 2 subunit gene is not deleted in velo-cardio-facial syndrome.
(54/620)
Velo-cardio-facial syndrome (VCFS) has been associated with schizophrenic symptoms in some patients and is caused by a deletion of 22q11.21--q11.23. The voltage-gated calcium channel (VGCC) gamma 2 subunit is located on chromosome 22 and is telemeric to the most commonly observed VCFS deletion region but is near a putative marker for schizophrenia (D22S278). Metaphase spreads of four controls, four patients with VCFS, and one patient with VCFS and schizophrenia were evaluated for the VCFS deletion using the VCFS-diagnostic probe, TUPLE 1, and for deletion of VGCC gamma 2 subunit gene using probes for that gene's exon 1 and exons 3 and 4. All of the VCFS patients had deletion of the TUPLE 1 probe on one chromosome of the chromosome 22 pair. None showed deletion of the gamma 2 subunit exons studied. The location of the gamma 2 subunit gene at 22q13.1 was confirmed by FISH in all cases. This study did not show a deletion of the gamma 2 subunit gene as a distinguishing feature of our patient with VCFS and schizophrenia. (+info)
Partial tetrasomy 12pter-12p12.3 in a girl with Pallister-Killian syndrome: extraordinary finding of an analphoid, inverted duplicated marker.
(55/620)
Cytogenetic analysis in a girl with multiple congenital anomalies indicating Pallister-Killian syndrome (PKS) showed a supernumerary marker chromosome in 1/76 lymphocytes and 34/75 fibroblast metaphases. GTG-banding pattern was consistent with the chromosomal region 12pter-12q11. While fluorescence-in-situ hybridisation (FISH) with a whole chromosome 12 painting probe confirmed the origin of the marker, a chromosome 12 specific alpha-satellite probe did not hybridise to it. FISH analysis with a specific subtelomeric probe 12p showed hybridisation to both ends of the marker chromosome. High-resolution multicolour-banding (MCB) studies revealed the marker to be a der(12)(pter-->p12.3::p12.3-->pter). Summarising the FISH information, we defined the marker as an inverted duplication of 12pter-12p12.3 leading to partial tetrasomy of chromosome 12p. In skin fibroblasts, cultured at the patient's age of 1 year and 9 years, the marker chromosome was found in similar frequencies, even after several culture passages. Therefore, we consider the marker to have a functional centromere although it lacks detectable centromeric alpha-satellite sequences. To the best of our knowledge, this is the first proven analphoid marker of chromosome 12. Molecular genetic studies indicated that this marker is of paternal origin. The finding of partial tetrasomy 12pter-12p12.3 in our PKS patient allows to narrow down the critical region for PKS. (+info)
The fourth dimension in simulation surgery for craniofacial surgical procedures.
(56/620)
The intracranial volume was measured in all 18 cases of craniosynostosis and craniofacial synostosis with 3DCT using a modification of Miyake's formula, with a 6 years' follow-up. 1: There were no cases where the intracranial volume was less than the modified Miyake's formula. 2: Total cranial reshaping, compared to the local forehead advancement, was effective in increasing the intracranial cavity and growth postoperatively. 3: In cases of craniofacial synostosis, there is a possibility that mental retardation will develop if the intracranial volume tends to increase rapidly and more than expected. (+info)