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Biomedical subjects

N Flanagan

Publications and source records attributed to N Flanagan.

16 recordsLinked to original sources
PubMed2000

Evidence for variable selective pressures at MC1R.

It is widely assumed that genes that influence variation in skin and hair pigmentation are under selection. To date, the melanocortin 1 receptor (MC1R) is the only gene identified that explains substantial phenotypic variance in human pigmentation. Here we investigate MC1R polymorphism in several populations, for evidence of selection. We conclude that MC1R is under strong functional constraint in Africa, where any diversion from eumelanin production (black pigmentation) appears to be evolutionarily deleterious. Although many of the MC1R amino acid variants observed in non-African populations do affect MC1R function and contribute to high levels of MC1R diversity in Europeans, we found no evidence, in either the magnitude or the patterns of diversity, for its enhancement by selection; rather, our analyses show that levels of MC1R polymorphism simply reflect neutral expectations under relaxation of strong functional constraint outside Africa.

Africa↗
PubMed1999

Genetic studies of the human melanocortin-1 receptor.

Genetic approaches have suggested a critical role for the melanocortin-1 receptor in the control of pigmentation. We showed that this gene is unusually polymorphic in European populations and that, of the many variants, three in particular appear to be associated with red hair or fair skin. Family studies suggest these are inherited as an autosomal recessive trait (or at least approximate to this in many families). To date all individuals with two of these three changes (homozygote or compound heterozygote) have red hair. Early functional studies are in keeping with defective signalling through MC1R. An interested and perhaps unexpected question relates to the evolutionary factors that have given rise to such variants. Two models can be proposed, that are based on multiple alleles with minor changes in function or genetic hitch-hicking.

Animals↗
PubMed1999

Low frequency of genetic change in p53 immunopositive clones in human epidermis.

Sun-exposed skin of Caucasians harbors thousands of p53-mutated clones, which are clinically invisible. Using whole mount immunostaining for p53 or Ki67 antigens, p53 sequencing, and loss of heterozygosity analysis, we have further characterised these clones. Loss of heterozygosity for the alleles examined is uncommon with the exception of 9q, which occurred in 28.3% of the samples. P53 clones are more common and larger in individuals with basal cell carcinoma than in control subjects (p < 0.03). Loss of heterozygosity is also more common in clones from individuals with basal cell carcinoma than in clones from subjects without a history of basal cell carcinoma, as would be expected if both relate to ultraviolet radiation exposure. p53 sequencing of clones is in keeping with the mutagenic role of ultraviolet radiation. Surprisingly, skin found to harbor p53 clones showed no clusters of Ki67 positive cells, unlike the situation for actinic keratoses or basal cell carcinomas. These results show that in human skin p53 mutation is not directly associated with genomic instability or abnormal cell cycling; that the p53 immunopositive clones are either genetically distinct or precursors to other squamous cell lesions of skin; and that p53 immunopositive clones are early lesions, in that gross disturbance of proliferation has not already occurred.

Aged↗
PubMed1998

Melanocortin 1 receptor variants in an Irish population.

The identification of an association between variants in the human melanocortin 1 receptor (MC1R) gene and red hair and fair skin, as well as the relation between variants of this gene and coat color in animals, suggests that the MC1R is an integral control point in the normal pigmentation phenotype. In order to further define the contribution of MC1R variants to pigmentation in a normal population, we have looked for alterations in this gene in series of individuals from a general Irish population, in whom there is a preponderance of individuals with fair skin type. Seventy-five per cent contained a variant in the MC1R gene, with 30% containing two variants. The Arg151Cys, Arg160Trp, and Asp294His variants were significantly associated with red hair (p = 0.0015, p < 0.001, and p < 0.005, respectively). Importantly, no individuals harboring two of these three variants did not have red hair, although some red-haired individuals only showed one alteration. The same three variants were also over-represented in individuals with light skin type as assessed using a modified Fitzpatrick scale. Despite these associations many subjects with dark hair/darker skin type harbored MC1R variants, but there was no evidence of any particular association of variants with the darker phenotype. The Asp294His variant was similarly associated with red hair in a Dutch population, but was infrequent in red-headed subjects from Sweden. The Asp294His variant was also significantly associated with nonmelanoma skin cancer in a U.K. population. The results show that the Arg151Cys, Arg160Trp, and Asp294His variants are of key significance in determining the pigmentary phenotype and response to ultraviolet radiation, and suggest that in many cases the red-haired component and in some cases fair skin type are inherited as a Mendelian recessive.

Adult↗
PubMed1998

Familial craniosynostosis, anal anomalies, and porokeratosis: CAP syndrome.

We report on the occurrence of coronal craniosynostosis, anal anomalies, and porokeratosis in two male sibs. A third male sib was phenotypically normal as were the parents. The occurrence of these three clinical features has, to our knowledge, not been reported before. Cutaneous or anal anomalies or both have been reported in a number of syndromes associated with craniosynostosis, including Crouzon, Pfeiffer, Apert, and Beare-Stevenson syndromes. These syndromes are associated with mutations in the fibroblast growth factor receptor genes FGFR1, FGFR2, and FGFR3. They are inherited in an autosomal dominant fashion. In contrast, the cases we report do not carry any of the common FGFR mutations and the pedigree suggests autosomal or X linked recessive inheritance.

Abnormalities, Multiple↗
PubMed1997

A family with hereditary spastic paraparesis and epilepsy.

PURPOSE: We describe a family with hereditary spastic paraparesis (HSP) in which 4 of 6 affected members also have epilepsy. METHODS: All family members were examined by 2 neurologists. Four affected and 3 unaffected family members had EEG recordings. Four affected members were investigated for other causes of spastic paraparesis and epilepsy. RESULTS: Epileptic symptoms varied among family members: 1 had complex partial seizures, another had focal myoclonic epilepsy, and 2 had simple partial seizures secondarily generalized. All 4 had clinical or EEG evidence to support a focal origin for the epilepsy, and 2 had photoparoxysal responses on EEG. Symptoms were more severe and occurred earlier in the younger generation, suggesting genetic anticipation in this family. The onset of epilepsy developed simultaneously with, or < or = 18 years before, onset of gait disturbance. Three unaffected family members had normal EEGs. CONCLUSIONS: The association of HSP and epilepsy should no longer be assumed to be fortuitous.

Adolescent↗
PubMed1997

Developmental enamel defects in tuberous sclerosis: a clinical genetic marker?

Ten probands with tuberous sclerosis (TS) and 20 first degree relatives were examined for evidence of pitted enamel hypoplasia; 100% of TS patients had pitting, compared to 65% of relatives and 72% of 25 controls. We found that 70% of TS cases had more than 14 pits per person compared with only 5% of relatives and 4% of controls; 85% of relatives and 84% of controls had fewer than six pits per person. Our results confirm that significantly increased numbers of dental enamel pits are found in persons with TS compared to controls. These results suggest that examination for the presence or absence of dental enamel pits is not a useful screening test for first degree relatives to detect otherwise unsuspected subjects with tuberous sclerosis. However, the lack of pits in first degree relatives in our study is probably largely because none of the relatives appeared to carry the TS gene.

Dental Enamel↗
PubMed1986

Clinical studies of chemonucleolysis patients with ten- to twenty-year follow-up evaluation.

A follow-up evaluation of 357 patients injected with chymopapain ten to 20 years earlier included 97 females of mean age 42.2 years and 260 males of mean age 41.6 years. Pain distribution and physical findings were positive for discogenic involvement of long duration prior to chemonucleolysis. Eighteen patients were treated under worker's compensation. Postoperation, significant back pain persisted less than 24 hours in seven patients, less than six days in 133, less than 21 days in 178, from one to three months in nine, and between three and six months in two patients. Leg pain remained less than 24 hours in 32 patients, between one and five days in 212, between six and 21 days in 96, between one and three months in seven, and between six and 12 months in three patients. Similar improvement in extensor hallucis longus weakness and straight leg raising was also noted. Pain relief in the long term showed none persisting in the 158 patients or 44%, mild remaining pain in 107 or 30%, moderate pain in 71 or 20% and some pain in 21 or 6%. Thus the result was graded satisfactory in 74%. Complications included thrombophlebitis in two, pulmonary emboli in two, severe abdominal stress two days postoperation in one, severe anaphylatic reaction in one, and transient chest pain of undetermined etiology in one patient. All made good recovery from these complications.

Activities of Daily Living↗
PubMed1983

Morphologic and morphometric studies of muscle in idiopathic scoliosis.

The gluteus maximus and paraspinal muscles in 15 cases of idiopathic scoliosis at the apex of the curve showed myopathic changes and a significant decrease in the type II fibers. Fiber type II atrophy was observed only on the concave side. Ultrastructure of paraspinal and gluteus muscle biopsies showed disruption of myofilaments, Z band streaming and subsarcolemmal accumulation of glycogen, lipid and mitochondria. Quantitative estimation of these subcellular organelles pointed out that a higher glycogen content was significant in both paraspinal as well as the gluteus muscles while a higher mitochondrial content was significant only on the convex side and the gluteus muscle but not the concave side of the apex when compared to normal quadriceps muscle. These findings suggest that idiopathic scoliosis is a diffuse disease process and may be considered a primary muscle disease.

Adolescent↗
PubMed1980

Neuropathy in thoracic scoliosis.

The erector spinae muscles of 20 normal humans were evaluated at C7, T3, T11, and L5 vertebral body levels bilaterally. At each level, the mean potential duration of the motor unit action potential was calculated. This control group was compared with a group of patients with C7 and L5 radiculopathy and with a group of patients with thoracic scoliosis. The mean potential durations of the radiculopathy group at the C7 and L5 levels were prolonged as were those values at the convex thoracic levels in the scoliotic group. Muscle biopsy of the erector spinae in the scoliotic group revealed grouped atrophy and changes consistent with a neuropathic process. A radiculopathic process was associated with idiopathic thoracic scoliosis and involved the convex side. It was maximal near the apex of the curve.

Action Potentials↗