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PubMed2003

Segregation analysis of prostate cancer in France: evidence for autosomal dominant inheritance and residual brother-brother dependence.

Four segregation analyses concerning prostate cancer (CaP), three conducted in the United States and one in Northern Europe, have shown evidence for a dominant major gene but with different parameter estimates. A recent segregation analysis of Australian pedigrees has found a better fit of a two-locus model than single-locus models. This model included a dominantly inherited increased risk that was greater at younger ages and a recessively inherited or X-linked increased risk that was greater at older ages. Recent linkage analyses have led to the detection of at least 8 CaP predisposing genes, suggesting a complex inheritance and genetic heterogeneity. To assess the nature of familial aggregation of prostate cancer in France, segregation analysis was conducted in 691 families ascertained through 691 CaP patients, recruited from three French hospitals and unselected with respect to age at diagnosis, clinical stage or family history. This mode of family inclusion, without any particular selection of the probands, is unique, as probands from all previous analyses were selected according to various criteria. Segregation analysis was carried out using the logistic hazard regressive model, as incorporated in the REGRESS program, which can accommodate a major gene effect, residual familial dependences of any origin (genetic and/or environmental), and covariates, while including survival analysis concepts. Segregation analysis showed evidence for the segregation of an autosomal dominant gene (allele frequency of 0.03%) with an additional brother-brother dependence. The estimated cumulative risks of prostate cancer by age 85 years, among subjects with the at-risk genotype, were 86% in the fathers' generation and 99% in the probands' generation. This study supports the model of Mendelian transmission of a rare autosomal dominant gene with high penetrance, and demonstrates that additional genetic and/or common sibling environmental factors are involved to account for the familial clustering of CaP.

Age of Onset↗
PubMed2002

Clinical and genetic epidemiology of inherited renal disease in Newfoundland.

Clinical and genetic epidemiology of inherited renal disease in Newfoundland. Newfoundland's geography, settlement, and socioeconomic development have produced a population useful for the study of genetic diseases. This review examines the clinical and genetic epidemiologic studies of inherited renal diseases undertaken in this population in the past 15 years. Common founder effects and large families through each generation provided very extensive pedigrees with autosomal-dominant diseases, such as polycystic kidney disease (PKD) and von Hippel-Lindau disease. In the former disease the diagnostic utility of renal ultrasound was determined, as was the prognostic impact of genotype, the role of the renin-angiotensin system in the pre-hypertensive phase, the potential for somatic mutations of the PKD2 gene, or the combination of mutations in the PKD1 and PKD2 genes, in single cells to induce cysts, and the demonstration that human transheterozygotes of PKD1 and -2 are not embryonically lethal. The presence of multiple genetic isolates and the high coefficient of kinship have predisposed to autosomal recessive diseases such as Bardet-Biedl syndrome (BBS), autosomal-recessive PKD, primary hyperoxaluria, and dihydroxyadenine urolithiasis. We have reported the clinical manifestations and natural history of the BBS, with particular emphasis on the fact that renal abnormalities are cardinal manifestations of the disease, the presence of at least six different genotypes, the identity and function of the BBS6 gene, and the presence of three different BBS6 mutations. Because of its relatively homogenous origins and high coefficient of kinship, Newfoundland's population also may be useful for the study of complex diseases such as preeclampsia. Using unbiased ascertainment and strict diagnostic criteria, we have found a significant risk of preeclampsia and non-proteinuric gestational hypertension in sisters of probands with preeclampsia, particularly when probands are defined by severity of preeclampsia, an observation that supports a study to search for susceptibility genes. We conclude that collaborations between clinical epidemiologists and molecular geneticists, using the Newfoundland population, have provided important clinical and mechanistic insights into inherited renal diseases.

Bardet-Biedl Syndrome↗
PubMed2005

Genetic testing for inherited colon cancer.

The genes associated with each of the inherited syndromes of colon cancer have now been identified, and genetic testing is available for diagnosis. These syndromes include familial adenomatous polyposis, hereditary nonpolyposis colorectal cancer, Peutz-Jeghers syndrome, juvenile polyposis syndrome, and, possibly, Cowden's syndrome. Clinical genetic testing approaches have been developed for each of these syndromes and are now a part of accepted clinical care. Disease-causing mutations can be found in the majority of families affected with one of the inherited syndromes, and, most importantly, once a mutation is found in an index case of the family, relatives can be tested for the presence or absence of that mutation with near 100% accuracy. Cancer screening and management in syndrome families is then based on the results of genetic testing. For the physician to order and properly interpret genetic tests, a basic understanding of the types of mutations that lead to inherited disease and the methods for detecting them is vital. These issues will be presented. Additional clinical issues somewhat unique to genetic testing include genetic counseling and informed consent for genetic testing, both of which will also be reviewed. Often the most difficult aspect of genetic testing is deciding which patients and families should undergo the testing. Furthermore, this issue is quite specific for each of the syndromes. Thus, following presentation of general principles of selection for genetic testing, a detailed approach for identifying persons who should undergo testing for each of the individual syndromes will be given, together with relevant descriptions of the syndromes. Finally, the ongoing work to discover new and possibly more common but less penetrant colon cancer susceptibility genes that cause common familial colon cancer will be presented.

Colonic Neoplasms↗
PubMed2002

Inherited thrombophilia and stillbirth.

Thrombophilias are inherited or acquired conditions that predispose individuals to thromboembolism. New inherited thrombophilias are recognized each year. Some, but not all, studies have found an association between inherited thrombophilias and adverse pregnancy outcomes, including fetal loss. The controversy regarding the clinical implications of thrombophilias in pregnancy is clouded by differences in study populations, the number of thrombophilias tested, interactions between thrombophilias, and the retrospective nature of most studies, just to name a few factors. The lack of adequately designed studies also extends to clinical management. Clear evidence to determine when to test, whom to test, which thrombophilias to test for, when to treat, and what to treat with is not available. Further studies to investigate these questions are urgently needed.

5,10-Methylenetetrahydrofolate Reductase (FADH2)↗
PubMed2001

Arrhythmogenic inherited heart muscle diseases in children.

The left ventricle (LV) plays a central role in the maintenance of health of children and adults due to its role as the major pump of the heart. In cases of LV dysfunction, a significant percentage of affected individuals develop signs and symptoms of congestive heart failure, leading to the need for therapeutic intervention. Therapy for these patients include anticongestive medications and, in some, placement of devices such as aortic balloon pump or left ventricular assist device, or cardiac transplantation. In the majority of patients the origin is unknown, leading to the term idiopathic dilated cardiomyopathy. During the past decade, the basis of LV dysfunction has begun to unravel. In approximately 30% to 40% of cases, the disorder is inherited; autosomal dominant inheritance is most common (although X-linked, autosomal recessive and mitochondrial inheritance occurs). In the remaining patients, the disorder is presumed to be acquired, with inflammatory heart disease playing an important role. In the case of familial dilated cardiomyopathy, the genetic basis is beginning to unfold. To date, 2 genes for X-linked familial dilated cardiomyopathy (dystrophin, G4.5) have been identified and 4 genes for the autosomal dominant form (actin, desmin, lamin A/C, delta-sarcoglycan) have been described. In 1 form of inflammatory heart disease, coxsackievirus myocarditis, inflammatory mediators, and dystrophin cleavage play a role in the development of LV dysfunction. This review describes the molecular genetics of LV dysfunction and provide evidence for a "final common pathway" responsible for the phenotype.

Arrhythmias, Cardiac↗
PubMed2002

The importance of cultural inheritance in psychiatric genetics.

Cultural inheritance, a genetic-based inheritance system transmitted by the brain, has previously been proposed to underlie normal behaviour and mental disorders. In cultural inheritance epigenetic mechanisms are involved in gene expression. This paper proposes that since there are marked epigenetic mechanisms involved in the expression of genes underlying primary (idiopathic) mental disorders, epimutations, rather than genetic mutations, underlie these disorders.

Animals↗
PubMed2003

[Non-invasive screening for GJB2 mutations in buccal smears for the diagnosis of inherited hearing impairment].

BACKGROUND: Approximately 1 out of 1000 children is affected by severe or profound hearing impairment at birth. In the last years it has been shown that more than 50 % of inherited prelingual, sensorineural hearing impairment may be attributed to genetic defects. Most commonly, the GJB2 gene (chromosome 13q11) that encodes connexin 26 (Cx26) is affected. Cx26 is crucial for the formation of gap junctions which play an important role in the intercellular exchange of electrolytes. A variety of autosomal recessive GJB2 mutations associated with inherited hearing impairment has meanwhile been identified. The most common GJB2 mutation in Caucasian populations, 35delG accounts for the majority of cases and has a carrier frequency of more than 2.5 %. Other distinct mutations account for hearing impairment in other parts of the world. MATERIAL AND METHODS: We examined in 59 Caucasian and Ghanaian individuals whether DNA recovered from buccal smears was appropriate for genetic testing by polymerase-chain reaction (PCR) based DNA-sequencing. RESULTS: Buccal smears could be taken conveniently in all cases, even from small babies. In 53 out of 59 samples the material recovered from buccal smears could be subjected to PCR of the second exon of the GJB2 gene and subsequent DNA-sequencing. GJB2 mutations were identified in 34 patients. 13 Caucasian individuals exhibited the most common mutation 35delG. In addition, four cases of the rare W24X and each one heterozygous case of the V153I- and the L90P mutation were found. In two African individuals the 35insG mutation was detected. All other African patients had mutations exclusively identified in Ghana so far with the exception of R143W. R143W accounts for most cases of profound deafness in Ghana and has been identified in low frequencies in other ethnic groups as well. CONCLUSION: Screening for GJB2 mutations in DNA recovered from buccal smears of individuals with inherited hearing impairment offers an easy, non-invasive method for early diagnosis and a basis of genetic counselling.

Adult↗
PubMed1984

Inherited chondrodysplasia punctata due to a deletion of the terminal short arm of an X chromosome.

We studied two families with an inherited deletion of the short arm of an X chromosome (Xp) in which affected male offspring have epiphyseal stippling in infancy (chondrodysplasia punctata), nasal hypoplasia, ichthyosis, and mental retardation. The presence of ichthyosis and the apparent pattern of X-linked recessive inheritance prompted investigation of the short arm of the X chromosome through studies of genetic markers and focused cytogenetic analysis. Biochemical studies suggested that there was a deletion of three genes previously mapped to the X-chromosome short arm, including the steroid sulfatase locus, the Xg locus, and the M1C2X locus. Prometaphase chromosomes demonstrated a deletion of Xp at p22.32 in the affected boys, in their obligate-carrier mothers, and in 11 of 25 women at risk as potential carriers. The women carrying the Xp deletion had normal gonadal function and fertility but were shorter than the noncarriers in their families (P less than 0.00001). These findings have implications for the genetic organization of this portion of the human X chromosome and demonstrate that small cytogenetic abnormalities may account for disorders with apparent mendelian patterns of inheritance.

Adolescent↗
PubMed2000

Clinical, biochemical, and genetic characterization of a novel estrogen-dependent inherited form of angioedema.

BACKGROUND: Two genetic forms of hereditary angioedema (HAE) are currently recognized. Both are transmitted in an autosomal dominant manner and are characterized by recurrent episodes of localized angioedema. Involvement of the gut leads to episodes of severe abdominal pain, and laryngeal involvement can lead to airway obstruction and even death. One type results from heterozygosity for a nonexpressed C1 inhibitor allele, and the other results from heterozygosity for a nonfunctional C1 inhibitor allele. OBJECTIVE: This report identifies a third type of HAE, with a unique estrogen-dependent phenotype. METHODS: Detailed medical histories were obtained from family members, and a pedigree was constructed to ascertain the mode of inheritance. Determination of serum complement factors, C1 inhibitor protein, C1 inhibitor function, coagulation factor XII, plasma prekallikrein, high molecular weight kininogen, and selected DNA sequences were performed in affected members by using standard assays. RESULTS: Episodes of angioedema were clinically indistinguishable from those associated with previously described forms of HAE; however, these occurred only during pregnancy or the use of exogenous estrogens. Patients were otherwise asymptomatic, except for one patient who had acetyl salicylic acid/nonsteroidal anti-inflammatory drug-related angioedema later in life. History was available for members spanning 4 generations, and affected individuals were identified in 3 generations. Of 46 family members, phenotype could be determined in 13 members. Seven were affected, and 6 were not. One male of undetermined phenotype was an obligate carrier. The unique estrogen-dependent nature of the phenotype means that the status of several members in the third and fourth generation remains unknown. The disorder appears to be transmitted in an autosomal dominant fashion, although other modes of inheritance cannot be excluded entirely. C1 inhibitor protein, C1 inhibitor function, C2, C4, C1q, coagulation factor XII, prekallikrein, and high molecular kininogen were normal in 3 affected family members during asymptomatic periods. DNA sequencing revealed no abnormality in 3 patients in the coding region of the gene encoding C1 inhibitor or in the 5' flanking regions of the genes encoding C1 inhibitor and factor XII. CONCLUSIONS: This family appears to have a novel form of inherited angioedema that does not result from C1 inhibitor deficiency or dysfunction. The phenotype is uniquely estrogen dependent. Implications for diagnosis and treatment are discussed. Further studies are required to define the exact nature of the genetic abnormality involved.

Adult↗
PubMed2003

Inherited thrombophilias are not increased in "idiopathic" small-for-gestational-age pregnancies.

OBJECTIVE: The purpose of this study was to determine (1). whether the inherited thrombophilias (the factor V Leiden and prothrombin gene mutations and the methylenetetrahydrofolate reductase [C677T] polymorphism) are increased in women with "idiopathic" (normotensive) small-for-gestational-age pregnancies and/or in their babies and (2). whether fetal carriage of a thrombophilia is associated with abnormal umbilical Doppler studies. STUDY DESIGN: This was a case-controlled study of normotensive women who were delivered of a singleton small-for-gestational-age baby (birth weight, <10th percentile adjusted for sex) with no clinical evidence of chromosomal or congenital abnormality. Control subjects were healthy women who were delivered of appropriate-for-gestational-age babies. RESULTS: One hundred forty-five women with small-for-gestational-age pregnancies and 290 control subjects were recruited. Small-for-gestational-age babies were born at an earlier gestational age (38 +/- 3.0 weeks) and with a lower birth weight (2373 +/- 521 g) than control babies (39.7 +/- 1.3 weeks and 3606 +/- 423 g, P <.01). There were no differences in the rates of factor V Leiden (2.8% vs 3.8%; relative risk, 0.79; 95% CI, 0.34-1.85), prothrombin gene mutation (2.8% vs 3.1%; relative risk, 0.92; 95% CI, 0.40-2.09), and methylenetetrahydrofolate reductase C677T polymorphism (13% vs 9%; relative risk, 1.27; 95% CI, 0.87-1.84) between mothers with small-for-gestational-age babies and control subjects, respectively. Inherited thrombophilias were not increased in small-for-gestational-age babies compared with control babies. Of small-for-gestational-age babies with abnormal umbilical artery Doppler studies (n = 25), 21% had a thrombophilia compared with 11% with normal umbilical artery Doppler studies (n = 68; relative risk, 1.75; 95% CI, 0.81-3.81). CONCLUSION: The rates of these inherited thrombophilias are not increased in normotensive women with small-for-gestational-age pregnancies. Further studies are required to determine whether thrombophilias are increased in small-for-gestational-age babies with abnormal umbilical Doppler study results.

Adult↗
PubMed2005

Telomere length and heredity: Indications of paternal inheritance.

Cellular telomere length is linked to replicative life span. Telomere repeats are lost in peripheral blood cells in vivo by age, and women show less telomere attrition than men. Previous reports have indicated that telomere length and chromosome-specific telomere-length patterns partly are inherited. The mode of heredity has not been clarified, but a link to the X chromosome was recently suggested. We analyzed peripheral mononuclear cells from 49 unrelated families for telomere length using a real-time PCR method. Short-term cultured Epstein-Barr virus-transformed lymphoblasts from the same individuals (n = 130) were analyzed for ability to maintain telomere length and possible gender-linked inheritance. A statistically significant association between telomere lengths comparing father-son (P = 0.011, n = 20) and father-daughter (P = 0.005, n = 22) pairs was found. However, no correlation was observed between mother-daughter (P = 0.463, n = 23) or mother-son (P = 0.577, n = 18). The father-offspring correlation was highly significant (P < 0.0001), in contrast to mother-offspring (P = 0.361). Epstein-Barr virus cultures demonstrated in most cases telomere preservation inversely related to initial mononuclear cell telomere length with short telomeres displaying the most pronounced elongation. Telomere length is inherited, and evidence for a father-to-offspring heritage of this trait was obtained, whereas in vitro telomere length maintenance was found to be dependent on the initial telomere length.

Adult↗
PubMed1969

Inheritance of nitrate reductase activity in Zea mays L.

Since the F(1) hybrid (B14 x Oh43) had been shown to have a higher (heterotic) level of nitrate reductase activity than either inbred parent (B14 or Oh43), studies were undertaken to determine the mode of inheritance. Standard methods for determining Mendelian inheritance were used to study segregation for level of nitrate reductase activity of individual plants. The genetic material used was the inbreds B14 and Oh43, F(1), F(1) backcrossed to both parents, F(2), F(3), and F(4) generations of the cross B14 x Oh43. The plant material was grown in the field and in growth chambers. It was shown that the maize inbreds B14 and Oh43 differ at two loci that control the level of nitrate reductase activity. Each inbred is homozygous for a dominant or partially dominant allele at one locus and homozygous recessive at a second locus. The locus at which B14 carries a dominant allele carries the recessive allele in Oh43. Oh43 has both a higher in vivo rate of synthesis of nitrate reductase and higher in vivo and in vitro loss of enzyme activity (decay) than B14. Thus, the rates of both enzyme synthesis and decay are factors governing the level of nitrate reductase activity in corn. The data suggest that the heterotic level of nitrate reductase activity in the F(1) hybrid is the result of inheritance of qualities that gives it "intermediate" rates of enzyme synthesis and decay.

Crosses, Genetic↗
PubMed1977

Segregation at a locus determining an immunoglobulin genetic marker for the light chain variable region affects inheritance of expression of an idiotype.

Previous investigations have demonstrated close genetic linkage between loci governing expression of strain-specific idiotypes and immunoglobulin heavy (H) chain allotype (i.e., the C(H) locus). This linkage is presumed to reflect polymorphism of V(H) genes (or of their expression) linked to the polymorphic C(H) locus. That there was no apparent involvement of light (L) chain loci (thought to be unlinked to H chain) in inheritance of the idiotype-positive (Id(+)) phenotype was surprising, because the L chain is required for formation of each of the idiotypes studied at the chemical level. However, previous studies involving backcrosses of F(1)(Id(+) x Id(-)) mice to the Id(-) parental strain have never employed as the Id(-) parent one of several inbred strains shown by G. M. Edelman and P. D. Gottlieb [(1970) Proc. Natl. Acad. Sci. USA 67, 1191-1199] to express a V(L)-region polymorphism. Among backcrosses performed in the present study, one involved the A/J strain as the Id(+) parent and the PL/J strain, one of the several strains with and L chain polymorphism, as the Id(-) parent. Whereas in three other backcrosses performed, idiotype expression segregated with H chain allotype, in the backcross to PL/J, all mice producing the characteristic A/J Id(+) phenotype were A/J allotype(+), but not all A/J allotype(+) mice were Id(+). Typing of backcross progeny for the Ly-3 thymocyte alloantigens, controlled by a locus closely linked to that governing the L chain polymorphism (called the VK-1 locus), indicated that only the Ly-3 heterozygotes expressed the characteristic A/J Id(+) phenotype. Thus, all Id(+) backcross mice inherited both the H chain allotype and the Ly-3 locus (and closely linked L chain-related locus) from the Id(+) A/J strain. This suggests that, when strains with L chain polymorphisms are included in genetic studies of idiotype expression, segregation of loci governing L chain expression may be found to contribute to inheritance of the Id(+) character. In addition, these studies may be taken as further evidence that the V(L)-region repertoire of the PL/J strain may differ considerably from that of most other inbred strains of mice.

Animals↗
PubMed1982

Clonal inheritance of the pattern of DNA methylation in mouse cells.

DNA-mediated gene transfer was used to investigate the mode of inheritance of 5-methylcytosine in mouse L cells. Unmethylated phi X174 replicative form DNA remains unmethylated after its introduction and integration into these cells. On the other hand, phi X174 replicative form DNA that was methylated in vitro at its C-C-G-G residues retains these methylations as shown by restriction enzyme analysis with Hpa II and Msp I to detect methylation at this specific site. Although these unselected methylated vectors are prone to lose 30-40% of their methyl moieties upon transfection, this demethylation appears to be random. Once established, the resulting methylation pattern is stable for at least 100 cell generations. In order to examine the specificity of methylation inheritance, fully hemimethylated duplex phi X174 DNA was synthesized in vitro from primed single-strand phi X174 DNA by using 5-methyl deoxycytidine 5'-triphosphate. This molecule was inserted into mouse L cells by cotransformation and subsequently was analyzed by a series of restriction enzymes. Only methylations located at C-G residues were conserved after many generations of cell growth. The results suggest that the inheritance of the cellular DNA methylation pattern is based on a C-G-specific methylase that operates on newly replicated hemimethylated DNA.

5-Methylcytosine↗
PubMed1989

Inheritance and expression of foreign genes in transgenic soybean plants.

DNA-coated gold particles were introduced into meristems of immature soybean seeds using electric discharge particle acceleration to produce transgenic fertile soybean plants. The lineages of integrated foreign DNA in two independently transformed plants were followed in the first (R(1)) and second (R(2)) generation of self-pollinated progeny. One plant (4615) was transformed with the Escherichia coli genes for beta-glucuronidase and neomycin phosphotransferase II; the other (3993) was transformed only with the gene for beta-glucuronidase. Segregation ratios for the introduced gene(s) were approximately 3:1 for plant 4615 and 1:1 for plant 3993 in the R(1) generation. DNA analysis showed 100% concordance between presence of the foreign gene sequences and enzyme activity. Moreover, all copies of the foreign genes are inherited as a unit in each plant. Plant 3993 segregated in a 1:1 ratio in the R(2) generation. R(1) plants derived from plant 4615, which expressed both genes, gave either 100% or 3:1 expression of both genes in the R(2) generation, demonstrating recovery of both homozygous and heterozygous R(1) plants. Our results show that foreign DNA introduced into soybean plants using electric discharge particle acceleration can be inherited in a Mendelian manner. Results also demonstrate cotransformation of tandem markers and show that both markers are inherited as closely linked genes in subsequent generations. These results indicate that whole plants can be derived from single transformed cells by a de novo organogenic pathway.

Journal Article↗
PubMed1992

Different missense mutations at the tissue-nonspecific alkaline phosphatase gene locus in autosomal recessively inherited forms of mild and severe hypophosphatasia.

Hypophosphatasia is a heritable form of rickets/osteomalacia with extremely variable clinical expression. Severe forms are inherited in an autosomal recessive fashion; the mode of transmission of mild forms is uncertain. The biochemical hallmark of hypophosphatasia is deficient activity of the tissue-nonspecific isozyme of alkaline phosphatase (TNSALP). Previously, we demonstrated in one inbred infant that an identical missense mutation in both alleles of the gene encoding TNSALP caused lethal disease. We have now examined TNSALP cDNAs from four unrelated patients with the severe perinatal or infantile forms of hypophosphatasia. Each of the eight TNSALP alleles from these four individuals contains a different point mutation that causes an amino acid substitution. These base changes were not detected in at least 63 normal individuals and, thus, appear to be causes of hypophosphatasia in the four patients. (Two additional base substitutions, found in one allele from each of the four patients, are linked polymorphisms.) Twenty-three unrelated patients (of 50 screened), who reflect the entire clinical spectrum of hypophosphatasia, possess one of our of the above eight mutations. In two of these additional patients, mild forms of the disease are also inherited in an autosomal recessive fashion. Our findings indicate that hypophosphatasia can be caused by a number of different missense mutations and that the specific interactions of different TNSALP mutant alleles are probably important for determining clinical expression. Severe forms, perinatal and infantile disease, are largely the result of compound heterozygosity for different hypophosphatasia alleles. At least some cases of childhood and adult hypophosphatasia are inherited as autosomal recessive traits.

Alkaline Phosphatase↗
PubMed1993

Inheritance of freezing resistance in tuber-bearing Solanum species: evidence for independent genetic control of nonacclimated freezing tolerance and cold acclimation capacity.

Frost or winter survival is regarded as a complex trait with polygenic inheritance. Two major components of this survival in crop plants are freezing tolerance in the nonacclimated state and cold acclimation capacity. To date researchers have not distinguished the two components as separate heritable traits. The mode of inheritance of these two traits was investigated in F1 and backcross populations of two wild diploid potato species (Solanum commersonii and Solanum cardiophyllum) exhibiting extremes of freezing tolerance and acclimation capacity. Precise assessment of these two traits allowed distinction of small but significant differences among genotypes. The two traits were not correlated in segregating populations, suggesting independent genetic control. Analyses of generation means indicate that all of the variance for acclimation capacity and a major proportion of the variance for the nonacclimated freezing tolerance can be best explained by an additive-dominance model with both traits being partially recessive. Recovery of parental phenotypes in limited populations suggests that both traits are controlled by relatively few genes. To our knowledge this is the first study demonstrating independent genetic control of the two main traits associated with frost or winter survival. Our results show that it should be possible to incorporate these traits from wild germ plasm into cultivated crop plants by independent selection. These results help explain the lack of progress in improving winter survival through field selection. Furthermore, our study demonstrates relative simplicity of the inheritance of cold acclimation, thus providing avenues for understanding the link between biochemical and genetic aspects of low-temperature stress in crop plants.

Journal Article↗
PubMed1998

Is pseudoexfoliation syndrome inherited? A review of genetic and nongenetic factors and a new observation.

Pseudoexfoliation (PEX) syndrome is the commonest identifiable cause of open-angle glaucoma worldwide. PEX is characterized clinically by small whitish deposits of fibrillar-granular material in the anterior segment of the eye. Despite its prevalence and potential for ophthalmic morbidity, surprisingly little is known about the etiology and pathogenesis of PEX. This article reviews the literature and presents evidence regarding genetic and nongenetic arguments for the etiology of pseudoexfoliation. Lines of evidence that support a genetic basis for PEX include transmission in two-generation families, twin studies, an increased risk of PEX in relatives of affected patients, and HLA studies. Nearly all pedigrees in the literature, and our own experience with PEX families in Iceland and Canada, suggest maternal transmission, raising the possibilities of mitochondrial inheritance, X-linked inheritance, and autosomal inheritance with genomic imprinting. A number of nongenetic factors have also been evaluated for their possible implication in the development of PEX. These include ultraviolet light, autoimmunity, slow virus infection, and trauma. It is possible that a combination of genetic and nongenetic factors may be involved in the etiology and pathogenesis of PEX, i.e. it may be a multifactorial disorder. Further studies with larger numbers of patients are needed to delineate more clearly the contribution of genetic (nuclear DNA, mitochondrial DNA or both) and nongenetic factors to the development of pseudoexfoliation syndrome and pseudoexfoliation glaucoma.

Autoimmunity↗