Analysis of candidate genes on chromosome 2 in oral cleft case-parent trios from three populations

Isolated oral clefts, including cleft lip with/without cleft palate (CL/P) and cleft palate (CP), have a complex and heterogeneous etiology. Case-parent trios from three populations were used to study genes spanning chromosome 2, where single nucleotide polymorphic (SNP) markers were analyzed individually and as haplotypes. Case-parent trios from three populations (74 from Maryland, 64 from Singapore and 95 from Taiwan) were genotyped for 962 SNPs in 104 genes on chromosome 2, including two well-recognized candidate genes: TGFA and SATB2. Individual SNPs and haplotypes (in sliding windows of 2-5 SNPs) were used to test for linkage and disequilibrium separately in CL/P and CP trios. A novel candidate gene (ZNF533) showed consistent evidence of linkage and disequilibrium in all three populations for both CL/P and CP. SNPs in key regions of ZNF533 showed considerable variability in estimated genotypic odds ratios and their significance, suggesting allelic heterogeneity. Haplotype frequencies for regions of ZNF533 were estimated and used to partition genetic variance into among-and within-population components. Wright's fixation index, a measure of genetic diversity, showed little difference between Singapore and Taiwan compared with Maryland. The tensin-1 gene (TNS1) also showed evidence of linkage and disequilibrium among both CL/P and CP trios in all three populations, albeit at a lower level of significance. Additional genes (VAX2, GLI2, ZHFX1B on 2p; WNT6-WNT10A and COL4A3-COL4A4 on 2q) showed consistent evidence of linkage and disequilibrium only among CL/P trios in all three populations, and TGFA showed significant evidence in two of three populations.

A case-control study of nonsyndromic oral clefts in Maryland

PURPOSE

Isolated, nonsyndromic oral clefts cases (n = 171) and unaffected controls (n = 182) were used to identify both genetic and environmental risk factors.

METHODS

Infants born in Maryland between 1992 to 1998 with an isolated, nonsyndromic oral cleft [cleft lip (CL), cleft lip and palate (CLP), or cleft palate (CP)] were recruited and exposure plus family history data were collected. Controls were unaffected infants. DNA was collected from all cases and their parents, plus controls.

RESULTS

No statistically significant association was found between any of the following: maternal smoking, vitamin use, urinary tract infection, or recreational drug use in either univariate analysis or after adjusting for maternal age and education. More control mothers reported alcohol use during the critical time period of pregnancy (one month before conception through the first trimester) as compared to case mothers. There was a 10-fold increase in risk to siblings of cases as compared to siblings of controls. Markers at four candidate genes were examined: transforming growth factor alpha (TGF alpha), transforming growth factor beta 3 (TGF beta 3), MSX1, and BCL3. Only MSX1 showed significant differences in allele frequencies between CP cases and controls. MSX1 also showed significant evidence of linkage disequilibrium with a susceptibility gene controlling risk for CP.

CONCLUSION

Most environmental risk factors examined here gave little evidence of association with risk to isolated, nonsyndromic oral clefts, although any alcohol consumption seemed protective. MSX1 showed evidence of linkage disequilibrium in both case-control and case-parent trio analysis.

Three-dimensional morphological analysis of isolated metopic synostosis

Morphological differences were quantified in three-dimensions among individuals with untreated isolated metopic synostosis and between those individuals and similar aged-matched normal dry skulls to test two hypotheses: first, that the dysmorphology is a self-correcting condition; and second, that a lack of vertical growth of the skull produces this dysmorphology. Three-dimensional (3D) coordinates were recorded for 22 craniofacial landmarks from CT scans of 15 metopic patients, ranging from 5- to 32-months-old, and of four normal dry skulls, ranging in age from 6- to 36-months-old. The patient population was diagnosed with isolated metopic synostosis at The Johns Hopkins Medical Institutions in Baltimore, Maryland or Children's Hospital in St. Louis, Missouri. Comparisons between the metopic age groups indicate that the trigonocephalic phenotype worsens through time. Between 5 and 14 months, the neurocranium displays an increase in vertical growth. This was followed by a lack of vertical growth between 14 and 32 months. The face displays a lack of vertical growth from 5 to 14 months and an increase in vertical growth after 14 months. Comparisons between the metopic age groups and the normal skulls indicate that the trigonocephalic head is taller superoinferiorly and longer anteroposteriorly. Relative to the normal phenotype, the inferior temporal region in the metopic phenotype is narrow. These findings enabled the rejection of both hypotheses and localized form differences between normal and metopic phenotypes. Based on these results, we suggest that the trigonocephalic phenotype worsens with age and the amount of vertical growth that produces the trigonocephalic phenotype varies throughout growth with respect to location within the skull and age.

Testing for interaction between maternal smoking and TGFA genotype among oral cleft cases born in Maryland 1992-1996

OBJECTIVE

Infants born in Maryland between June 1992 and June 1996 were used in a case-control study of nonsyndromic oral clefts to test for effects of maternal smoking and a polymorphic genetic marker at the transforming growth factor alpha (TGFA) locus, both of which have been reported to be risk factors for these common birth defects.

DESIGN AND SETTING

Cases were infants with an oral cleft ascertained through three comprehensive treatment centers, with additional ascertainment through a registry of birth defects maintained by the Maryland Health Department. Controls were healthy infants. Medical history information on infants and mothers were collected, along with DNA samples.

PATIENTS, PARTICIPANTS

Among 286 cases contacted (72% ascertainment), there were 192 nonsyndromic isolated oral clefts (106 M; 86 F) available for this case-control study.

MAIN OUTCOME MEASURES

The largest group of 149 Caucasian nonsyndromic cases and 86 controls was used to test for association with maternal smoking and genotype at the Taq1 polymorphism in TGFA.

RESULTS

While this modest sample had limited statistical power to detect gene-environment interaction, there was a significant marginal increase in risk of having an oral cleft if the mother smoked (odds ratio = 1.75, 95% CI = 1.01 to 3.02). We could not demonstrate statistical interaction between maternal smoking and TGFA genotype in this study, however, and the observed increase in the C2 allele among cases was not statistically significant.

CONCLUSIONS

We could not confirm either the reported association between oral clefts and TGFA genotype or its interaction with maternal smoking. However, these data do show an increased risk if the mother smoked during pregnancy, and this effect was greatest among infants with a bilateral cleft and no close family history of clefts.

Rigid fixation of internal orbital fractures

When large portions of the internal orbit are destroyed (two to four walls), standard bone-grafting techniques for immediate and late orbital reconstruction may not yield predictable eye position. Critical bone support is most often deficient inferomedially. CT analysis of orbital volume in cases where eye position was unsatisfactory reveals that displacement of bone grafts is one mechanism of the unsatisfactory result. Other mechanisms include undercorrection and bone-graft resorption. In order to minimize postoperative bone-graft displacement, titanium implants were used to span large defects in the internal orbit to provide a platform for bone-graft support. Twenty-six implants were placed in immediate and 12 were placed in late orbital reconstructions. More reliable bone-graft position resulted. Two late infections have occurred resulting in implant removal in a 3-year period.

The redistribution of collagen in expanded pig skin

Silicone tissue expanders were inserted subcutaneously in the buttocks of nine young pigs and gradually inflated to maximum capacity over 5 weeks. On the control side the expanders were left uninflated. Island buttock flaps were then raised, the expanders removed and the flaps spread into the same sites for 10 days. The tissue was harvested. Area measurements and full thickness skin biopsies were taken 10 days after flap inset in order to study the changes in collagen composition and isotypes in the skin layers. Ten days after inset of the flap the expanded skin had a mean 47% increase in surface area, was 9% thinner (from surface to implant), mostly due to thinning of the subcutaneous zone, but was not significantly different in water content, relative to the control skin. The expanded skin had a significant 9.3% increase (p less than 0.01, t test) in collagen content of the dermis. The relative proportions of Types I and III were not significantly changed by skin expansion in either the dermal/epidermal or subcutaneous/capsular zones. It is speculated that tensile factors during expansion stimulate the biosynthetic activity and/or mitotic activity of fibroblasts in the dermis to produce this gain in collagen in the expanded compared with unexpanded tissue.

Comparative viability of expanded and unexpanded axial pattern skin flaps in pigs

A comparison of viable areas of axial pattern flaps post inset was made between expanded and non-expanded pig buttock island flaps. The deep circumflex iliac artery and vein supply approximately the proximal 14 x 10 cm area of this flap. Larger flaps were raised on expanded and control sides of eight pigs to determine if expansion increased the area of survival. In six of eight pigs whose initial tissue expansion did not create more than approximately a 50% increase in skin area, the expanded flaps had a statistically significant increase in viable skin area (proportionally) 10 days post inset than their control flaps (p less than 0.05). Two other pigs did not conform to this pattern. Their initial tissue expansion was greater than 50%, and the resulting area of flap viability was proportionally less in expanded flaps than the control flaps.

Changes in area and thickness of expanded and unexpanded axial pattern skin flaps in pigs

The pig buttock flap model was used firstly, to compare changes in expanded axial skin flap area with control flaps prior to flap elevation and 3 or 4 months post-flap inset and, secondly, to compare the thickness of expanded and control flaps at elevation and for 3 to 6 months post-flap inset. Following 5 weeks' expansion and prior to elevation, the expanded tissue had gained a significant 63.3% mean increase in area compared with the control tissue (p less than 0.01). Immediately post elevation and inset, the expanded flaps were still significantly larger than the control flaps by a mean 29.8% (p less than 0.01) but had lost 56% of the original area gained. Little change in area occurred in the 3 months post-flap inset as the expanded flaps were still a mean 23.4% larger than the control (p less than 0.01). Dermal and cellular non-keratinised epidermal layers thickened markedly in expanded skin compared to control skin. Following elevation and inset of the flaps, both dermis and epidermis thickened in expanded and control flaps.

Protein metabolism and fibrosis in experimental canine obstructive lymphedema

Obstructive lymphedema is a pathologic condition resulting in the accumulation and stagnation of serum proteins in the lymphatics and interstitial spaces. In a canine model of obstructive lymphedema, one limb was rendered lymphedematous, and various biochemical parameters were determined in this and an unaffected control limb. Both lymph and interstitial fluid had significantly decreased acid proteinase activity (comprising mostly cathepsin D-like enzymes) and neutral proteinase activity (comprising metallo, sulfhydryl, and serine proteinases, and collagenase). Possible reasons for these decreases could be: (1) saturation of macrophages and their surrounding environment with whole or partially digested proteins, or (2) elevation in the levels of circulating inhibitors like alpha 2-macroglobulin. The lymphedematous skin was significantly thicker than control skin and had elevated levels of collagen. However, unlike some fibrotic conditions, the relative proportions of types I, III, and V collagen, as determined by pepsin solubilization and neutral salt fractionation of the collagen fibrils, were similar to those found in normal skin. It is speculated that a decrease in the breakdown of collagen by collagenase and a continuing synthesis of collagen by fibroblasts led to an imbalance in favor of collagen deposition in the skin.

The free radial forearm flap with and without bone for closure of large palatal fistulae

Three cases of palatal fistulae closed by microvascular transfer of radial forearm flaps are presented. Vascularised bone was included in one flap and all operations were free of complications. Facial scarring is minimal and the secondary deformity in the arm has not been significant. It is suggested that this procedure presents fewer difficulties than other techniques for treating the large palatal fistula and may prevent the collapse of the alveolar arch which follows the scarring associated with closure by local tissue.