Jodie N. Painter

A 4-bp Deletion in the Birt-Hogg-Dubé Gene (FLCN) Causes Dominantly Inherited Spontaneous Pneumothorax

Primary spontaneous pneumothorax (PSP), a condition in which air enters the pleural space and causes secondary lung collapse, is mostly sporadic but also occurs in families. The precise etiology of PSP remains unknown, although it is associated with emphysemalike changes (bullae) in the lungs of almost all patients. We describe the results of a genetic study of a large Finnish family with a dominantly inherited tendency to PSP. A genomewide scan suggested linkage to chromosome 17p11. Screening of the best candidate gene, FLCN, revealed a 4-bp deletion in the first coding exon, which causes a frameshift that predicts a protein truncation 50 missense amino acids downstream. All carriers of the deletion had bullous lung lesions. Mutations in FLCN are also responsible for Birt-Hogg-Dubé (BHD) syndrome (a dominantly inherited disease characterized by benign skin tumors, PSP, and diverse types of renal cancer) and, rarely, are detected in sporadic renal and colorectal tumors. Unlike other FLCN mutations, the exon 4 deletion seems to be associated with bullous lung changes only with 100% penetrance. These results suggest that changes in FLCN may have an important role in the development of PSP and, more importantly, of emphysema, a chronic pulmonary disease that often leads to formation of bullous lesions and lowered pulmonary function. Additionally, given the strong association of PSP and BHD, the connection between these conditions needs to be investigated further, particularly in patients with familial PSP, who may be at a greater risk of developing renal cancer.

Sequence variation in the ATP8B1 gene and intrahepatic cholestasis of pregnancy.

Intrahepatic cholestasis of pregnancy (ICP) is a cholestatic condition that may affect women during the third trimester of pregnancy. Symptoms experienced by these women generally resolve spontaneously following delivery, but prior to delivery the fetus is at increased risk of intrauterine distress and sudden intrauterine death. The genetic etiology of most cases of ICP is unknown, although heterozygous carriers of mutations causing progressive familial intrahepatic cholestasis (PFIC) diseases may experience ICP. When examining linkage to known cholestasis genes, affected members of four Finnish ICP families shared haplotypes around ATP8B1, the gene responsible for PFIC1. This gene was subsequently screened in 176 familial and sporadic ICP patients. A total of 17 sequence changes were detected, five exonic and 12 intronic. No intronic change was associated with ICP in sporadic cases. Four intronic changes segregated with ICP in three families, a different change in each of two families and three changes in another family, although the significance of this is currently unknown. Three exonic changes were nonsynonymous, one (in exon 23) is probably a polymorphism while two predict novel amino-acid replacements (N45T and K203R). These changes, in exons 2 and 7, were detected in one individual each, and may have predisposed these individuals to ICP. In conclusion, although the exon 2 and 7 changes may have functioned as risk alleles, ATP8B1 is probably not a major gene contributing to the occurrence of ICP.

Genetic features of the X chromosome affect pubertal development and testicular degeneration in adolescent boys with Klinefelter syndrome

Objective  To investigate how genetic features of the X chromosome influence growth, pubertal development and testicular degeneration in adolescent boys with Klinefelter syndrome (KS). Previous studies have suggested that genetic features of the X chromosome may contribute to the wide phenotypic variation in KS.

Sex chromosome characteristics and recurrent miscarriage

OBJECTIVE To investigate whether skewed X chromosome inactivation (XCI) and Y chromosome microdeletions are associated with recurrent miscarrige (RM). DESIGN A retrospective study. SETTING University hospital and genetic laboratory. PATIENT(S) Altogether, 46 women with a history of RM, defined as at least three miscarriages, and a control group of 95 women with no history of miscarriage were included in the XCI study. In the Y chromosome microdeletion study 40 male partners of women with RM were studied. INTERVENTION(S) Blood samples for DNA extraction. MAIN OUTCOME MEASURE(S) X chromosome inactivation patterns in the females were analyzed using a methylation-sensitive assay. The DNA from males was tested for Y chromosome microdeletions by analyzing 37 sequence tagged sites. RESULTS Mildly skewed XCI (>85% inactivation of one allele) was detected in 4 of 43 (9.3%) patients, and 9 of 81 (11.1%) controls. Among these women, extremely skewed XCI (>90% inactivation of one allele) was detected in 2 of 43 (4.7%) patients, and 4 of 81 (4.9%) controls. No statistical differences could be shown between the groups. No microdeletions were found in the male partners. CONCLUSION(S) The frequency of both extremely and mildly skewed XCI was similar in patients and control women. Y chromosome microdeletions were not found in spouses of patients. Based on these results we conclude that skewed X inactivation and Y chromosome microdeletions are not associated with RM in our study couples.

Study of p53 gene mutations and placental expression in recurrent miscarriage cases

This study aimed to investigate the role of p53 in early human development by screening patients with recurrent miscarriages (RM) for mutations in the p53 gene and by studying p53 expression in placental tissue. A total of 46 women with RM and 191 control women were included in the study. A sample was also obtained from 40 male partners of RM patients. The samples were screened for p53 sequence variations using denaturing high-performance liquid chromatography, sequencing and allele-specific polymerase chain reaction. Placental tissue was available from 19 miscarriages. p53 expression in placental tissue was studied by immunohistochemical staining. The C11992A polymorphism in p53 was found to be associated with RM in Finnish patients. The C/A or A/A genotype was detected in 32.6% of the women with RM and in 18.9% of the controls (P = 0.0414, odds ratio 2.083, confidence interval 1.018-4.259). The results suggest that women carrying the C/A or A/A genotype have a two-fold higher risk for RM than women with the C/C genotype. Further studies are, however, necessary to define whether the intronic polymorphism has functional consequences. The immunohistochemical staining of placental tissues revealed no abnormal p53 expression patterns in the samples studied.

A known polymorphism in the bile salt export pump gene is not a risk allele for intrahepatic cholestasis of pregnancy

Eloranta et al. (1) recently reported an association between a single nucleotide polymorphism (SNP) (rs473351) in the untranslated region of exon 28 of the bile salt export pump (BSEP, now ABCB11) and the occurrence of intrahepatic cholestasis of pregnancy (ICP) in a cohort of Finnish women. Furthermore, an A-G haplotype, formed by the common allele of an intron 19 SNP (rs853782) and the exon 28 SNP, was over-represented in ICP patients in comparison with matched controls. Both the ICP and control groups were relatively homogeneous, comprising women originating from the same region in eastern Finland. We have now tested for an association between the exon 28 SNP and ICP in a larger, more heterogeneous group of Finnish women.

Genetic differentiation Within metapopulations of Euphydryas aurinia and Melitaea phoebe in China

We analyzed genetic differentiation within metapopulations of two species of checkerspot butterfly, Euphydryas aurinia and Melitaea phoebe, in China. To generate genetic information, we used a new molecular technique, DALP – direct amplified length polymorphism. AMOVA results showed that most of the variation occurred among individuals within local populations of both E. aurinia and M. phoebe. However, while there was differentiation among local population in E. aurinia (P < 0.001), there was no subdivision in metapopulation of M. phoebe (P = 0.210). This is consistent with the behavior of M. phoebe adults being more dispersive than E. aurinia. Within the M. phoebe metapopulation, three neighboring patches were always occupied during the observation period (1998–2000). In addition, the number of individuals in these three populations accounted for the majority of M. phoebe larvae, and hence we conclude that the M. phoebe metapopulation might exist as a source-sink metapopulation. On the other hand, the E. aurinia metapopulation is an example of a classical metapopulation. Therefore, the conservation management of these two species should reflect these differences.

Amplification of DNA markers from scat samples of the least weaselMustela nivalis nivalis

To test the feasibility of using field-collected scats as a source of DNA in the study of the least weaselMustela nivalis nivalis Linnaeus, 1766, DNA was extracted from scat samples collected from captive weasels using a modified extraction protocol. Using universal primers, the control region of the mitochondrial genome was successfully amplified from scat-extracted DNA. This amplification resulted in two products; one equivalent in size and sequence to the product obtained from tissue-extracted weasel DNA, and the other slightly larger and equivalent in size and sequence to the domestic house mouseMus musculus, the food source of the captive weasels. This demonstrates the reliability of DNA extraction from scats, as well as the possibility, under favourable circumstances, of identifying the prey species from the same samples. In addition, we attempted to amplify microsatellite loci from both tissue and scat-extracted DNA using six primer pairs designed for other mustelids, the American minkMustela vison and the wolverineGulo gulo. While three loci, Mvi57 (American mink), Ggu216 and Ggu234 (wolverine), were found to be polymorphic in the least weasel, amplification of these loci from the scat extracted DNA was only successful for approximately half of the samples. Although further work is needed, the present results suggest that it is possible to use scats as a source of DNA in field studies of the least weasel.

Does the Y chromosome have a role in Müllerian aplasia

OBJECTIVE To investigate whether Y chromosomal genetic material has a role in the development of Müllerian aplasia in Finland. We have studied the TSPY1 gene and 38 additional male-specific fragments covering areas of both the long and short arms of the Y chromosome in Finnish patients with Müllerian aplasia. DESIGN A retrospective study. SETTING University hospital and genetic laboratory. PATIENT(S) A sample set of 110 Finnish patients with well-diagnosed Müllerian aplasia and 20 healthy relatives (13 mothers, 4 fathers, and 3 sisters from different families) were included in the study. One hundred healthy female controls with a background of at least one normal pregnancy with delivery were used as controls. INTERVENTION(S) Blood samples for DNA extraction. MAIN OUTCOME MEASURE(S) Detection of Y chromosomal fragments by polymerase chain reaction in female patients with Müllerian aplasia. RESULT(S) None of the female patients showed presence of the earlier reported TSPY1 gene or 38 additional Y chromosomal markers. CONCLUSION(S) Our results indicate that the studied Y-specific fragments, namely TSPY1 and 38 Y chromosomal markers, are not responsible for the syndrome in these Finnish patients with Müllerian aplasia.