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Complex patterns of inheritance of an imprinted murine transgene suggest incomplete germline erasure.

Here we report a transgenic mouse line that exhibits significant deviations from a classic pattern of parental imprinting. When the transgene is passed through the female germline, it is completely silenced in some offspring while in others expression is reduced. This variable expressivity does not appear to be the result of differences in the presence of unlinked modifiers. Female transmission of the transgene is associated with hypermethylation. The transgene is generally reactivated on passage through the male germline. Extended pedigrees reveal complex patterns of inheritance of the phenotype. The most likely explanation for this result is that the imprint is not completely erased and reset when passed through the germline of either sex. FISH analysis reveals that the transgene has integrated into chromosome 3 band E3, a region not known to carry imprinted genes, and the integration site shows no sign of allele-specific differential methylation. These findings, in conjunction with other recent work, raise the possibility that the introduction of foreign DNA into the mammalian genome, either through retrotransposition or transgenesis, may be associated with parental imprinting that is not always erased and reset during meiosis.

Animals↗

Glycine substitutions in the triple-helical region of type VII collagen result in a spectrum of dystrophic epidermolysis bullosa phenotypes and patterns of inheritance.

The dystrophic forms of epidermolysis bullosa (DEB) are characterized by fragility of the skin and mucous membranes. DEB can be inherited in either an autosomal dominant or autosomal recessive pattern, and the spectrum of clinical severity is highly variable. The unifying diagnostic hallmark of DEB is abnormalities in the anchoring fibrils, which consist of type VII collagen, and, recently, mutations in the corresponding gene, COL7A1, have been disclosed in a number of families. In this study, we report six families with glycine substitution mutations in the triple-helical region of type VII collagen. Among the six families, two demonstrated a mild phenotype, and the inheritance of the mutation was consistent with the dominantly inherited form of DEB. In the four other families, the mutation was silent in the heterozygous state but, when present in the homozygous state, or combined with a second mutation, resulted in a recessively inherited DEB phenotype. Type VII collagen is, therefore, unique among the collagen genes, in that different glycine substitutions can be either silent in heterozygous individuals or result in a dominantly inherited DEB. Inspection of the locations of the glycine substitutions along the COL7A1 polypeptide suggests that the consequences of these mutations, in terms of phenotype and pattern of inheritance, are position independent.

Adult↗

Pattern of inheritance of microsatellite loci in the squid Loligo pealeii (Mollusca: Cephalopoda).

Six microsatellite loci are described for the squid Loligo pealeii. All loci exhibit some degree of allelic diversity. The pattern of inheritance was tested for 3 loci through an analysis of the filial genotypes from a female-male mating. At all 3 loci, the ratios of the filial genotypes conformed to the ratios expected by Mendelian inheritance. The hypervariable loci will be useful in studies on sexual selection in this species, whereas the relatively less variable loci will be useful to address questions of population structure.

Journal Article↗

Epidemiology and genetic theories in the etiology of congenital talipes equinovarus.

The exact genetic mechanism of inheritance of congenital talipes equinovarus (CTEV) has been extensively investigated using family studies and other epidemiological methods, but to date no conclusive result has been reached. This may be due to the presence of a number of inheritance patterns, a number of different etiologies presenting as the same morphological condition, or complex gene-environment interactions. Indeed, a number of epidemiological factors have also been implicated in the etiology. While epidemiological studies can suggest inheritance patterns, only by identification of specific genes, can inheritance patterns be proven. This article reviews the epidemiological work on the etiology of CTEV and discusses some of the epidemiological principles involved.

Clubfoot↗

Clinical management of a child with Prader-Willi Syndrome from maternal uniparental disomy (UPD) genetic inheritance.

UNLABELLED: Prader-Willi Syndrome (PWS) is reported in 1 in 10,000-15,000 individuals. Unfortunately, many cases are missed due to clinicians' lack of familiarity with the syndrome as well as clinical and laboratory diagnostic criteria. Although common clinical characteristics are reported, variety exists in the nature and severity of dysfunction associated with PWS. Case studies can provide information to understand relationships between phenotypic characteristics and genetic inheritance, which can in turn lead to effective clinical management. The purpose of this case study was to describe the characteristics of a child with PWS due to maternal uniparental disomy inheritance pattern and to describe clinical management and treatment outcomes. LEARNING OUTCOMES: The reader will obtain information about: (1) the genetic inheritance patterns and clinical characteristics of Prader-Willi Syndrome, (2) genotypic/phenotypic relationships specific to Prader-Willi Syndrome, and (3) clinical implications, management, and outcomes in a case description of a child with PWS due to maternal uniparental disomy inheritance pattern.

Articulation Disorders↗

Analysis of the patterns of inheritance of splenomegaly and serum IgM levels in the Watut of Papua New Guinea.

Hyperreactive malarious splenomegaly (HMS) reflects abnormal immune responses to malarial infection. The central question is whether HMS results from unusual patterns of malarial infection or from immune incompetence in the host. Family distributions of two features of the syndrome, splenomegaly and excessively high IgM levels, have been examined in a Papau New Guinea population in which HMS is exceptionally common. Segregation analysis of spleen grade shows that a major sex-linked gene controls hyperresponsiveness to malaria. This finding is supported by additional segregation analysis, which shows that an autosomal locus cannot account for a significant proportion of variation in spleen grade, and by path analysis, which rejects a model that assumes that parents contribute equally to the child's genotype. The sex-linked gene contributing to HMS was not mediated through sex linkage of a major gene for IgM concentrations, as shown by segregation analysis. It has yet to be determined whether this pattern of inheritance also applies to HMS occurring sporadically in other less severely affected populations. The applicability of these findings to the general variability in "normal" IgM responses to malaria also remains to be established.

Adult↗

The inheritance of vertebral shape in the mouse. I. A study using Fourier analysis to examine patterns of inheritance in the morphology of cervical and upper thoracic vertebrae.

The shapes of cervical and upper thoracic vertebrae from large samples of 2 inbred strains of mice and their F1 offspring were examined using Fourier analysis to investigate in detail the distributions and magnitudes of differences in vertebral shape between different strains of mice, the relationships between parents and offspring and any differences in the inheritance of vertebral shape between successive vertebral levels. Consistent with the findings of an earlier study there was evidence for considerable differences between vertebral levels in the degree to which offspring resemble one or other parent. The results demonstrate that the inheritance of vertebral morphology conforms to a model in which F1s between inbred strains form a triangular relationship with their parents. Furthermore, this relationship varies between vertebral levels. The significance of these findings is considered in relation to the understanding of the mechanisms of character inheritance and evolution and some new directions for research into vertebral column morphogenesis are proposed.

Animals↗

Applied genetics for the practicing optometrist.

A good preventive blindness program includes a strong program in genetic counseling. Optometrists can be of substantial assistance to a genetic counseling program by: 1) being informed of the various types of inherited ocular disorders, and their modes of transmission. 2) becoming aware of the presence of disorders in other members of the patient's family, and 3) encouraging the affected family members to seek genetic counseling prior to conception. This article is designed to serve as a guide for familiarizing the practicing O.D. with the various types of inheritance patterns, specific disorders which follow these inheritance patterns, and some of the ocular and systemic characteristics of the disorders. Only those anomalies of structure and/or function which have an identifiable (and therefore a predictable) genetic mode of transmission will be discussed. This article is intended to serve as a brief and general review of some of the more common ocular disorders, and not as a comprehensive text on the genetics of ophthalmic diseases. Emphasis is placed on the optometric management of each disease discussed.

Child↗

Familial auditory neuropathy.

OBJECTIVES/HYPOTHESIS: Auditory neuropathy is a sensorineural hearing disorder characterized by absent or abnormal auditory brainstem responses and normal cochlear outer hair cell function as measured by otoacoustic emission recordings. Many risk factors are thought to be involved in its etiology and pathophysiology. Four Chinese pedigrees with familial auditory neuropathy were presented to demonstrate involvement of genetic factors in the etiology of auditory neuropathy. STUDY DESIGN: Probands of the above-mentioned pedigrees, who had been diagnosed with auditory neuropathy, were evaluated and followed in the Department of Otolaryngology-Head and Neck Surgery, China People Liberation Army General Hospital (Beijing, China). Their family members were studied, and the pedigree maps established. METHODS: History of illness, physical examination, pure-tone audiometry, acoustic reflex, auditory brainstem responses, and transient evoked and distortion-product otoacoustic emissions were obtained from members of these families. Some subjects received vestibular caloric testing, computed tomography scan of the temporal bone, and electrocardiography to exclude other possible neuropathic disorders. RESULTS: In most affected patients, hearing loss of various degrees and speech discrimination difficulties started at 10 to 16 years of age. Their audiological evaluation showed absence of acoustic reflex and auditory brainstem responses. As expected in auditory neuropathy, these patients exhibited near-normal cochlear outer hair cell function as shown in distortion product otoacoustic emission recordings. Pure-tone audiometry revealed hearing loss ranging from mild to profound in these patients. Different inheritance patterns were observed in the four families. In Pedigree I, 7 male patients were identified among 43 family members, exhibiting an X-linked recessive pattern. Affected brothers were found in Pedigrees II and III, whereas in pedigree IV, two sisters were affected. All the patients were otherwise normal without evidence of peripheral neuropathy at the time of writing. CONCLUSION: Patients with characteristics of nonsyndromic hereditary auditory neuropathy were identified in one large and three smaller Chinese families. Pedigree analysis suggested an X-linked, recessive hereditary pattern in one pedigree and autosomal recessive inheritances in the other three pedigrees. The phenotypes in the study were typical of auditory neuropathy; they were transmitted in different inheritance patterns, indicating clinical and genetic heterogeneity of this disorder. The observed inheritance and clinical audiological findings are different from those previously described for nonsyndromic low-frequency sensorineural hearing loss. This information should facilitate future molecular linkage analyses and positional cloning for the relative genes contributing to auditory neuropathy.

Adolescent↗

Patterns of inheritance of mating signals in interspecific hybrids between sailfin and shortfin mollies (Poeciliidae: Poecilia: Mollienesia).

Differences in male morphology and mating behaviors are thought to confer species sexual isolation between sailfin and shortfin species of mollies. This study used interspecific crosses between the sailfin molly, P. latipinna, and the shortfin molly, P. mexicana, to investigate patterns of inheritance of morphological traits and behavioral rates of three mating behaviors in F1 hybrid males. The two parental species showed clear species differences with respect to the length of the dorsal fin and dorsal fin ray number. First generation hybrid males were intermediate between the two parental species for dorsal fin length and fin ray number, suggesting autosomal control of this trait with little effect of dominance by genes from either parental species. Parental species showed clear species differences in their rates of courtship displays. Unlike the pattern for dorsal fin morphology, F1 hybrid males showed a clear distinction in display rates with respect to the direction of the interspecific cross. Male hybrids whose sires were P. latipinna had courtship display rates that were up to three times higher than the rates of displays performed by hybrid males whose fathers were P. mexicana. The distribution of phenotypes between the parental species and that of hybrid males sired by that parental species was nearly identical. Such a pattern suggests the influence of Y-linked genes on the inheritance of courtship display rates in mollies.

Animals↗

Patterns of inheritance in hypertrophic cardiomyopathy: assessment by M-mode and two-dimensional echocardiography.

To determine the mode of inheritance of hypertrophic cardiomyopathy (HC), 367 relatives from 70 families with HC were studied by M-mode and 2-dimensional echocardiography (2-D echo). Inspection of individual family pedigrees suggested that HC was genetically transmitted in 39 pedigrees (56%) and probably sporadic in 31 (44%). Of the 39 pedigrees with familial occurrence, 30 had patterns of inheritance that were most consistent with autosomal dominant transmission. A complex mathematical pedigree analysis determined that patterns of genetic transmission observed in the overall study group were not consistent with known models of autosomal dominant, autosomal recessive, or X-linked inheritance and did not support a unified concept of single-gene Mendelian transmission for all families. The proportion of first-degree relatives affected by HC was 22%, with HC most common in fathers of the proband and least common in offspring. About 20% of the affected relatives (10 of 53) appeared to have inherited a "subclinical" form of HC, in which the sole evidence of HC was the morphologic expression detectable only with echocardiography. Probands and affected relatives differed distinctly with regard to the expression of HC. Probands most often showed functional limitation (81%), subaortic obstruction at rest (53%), particularly diffuse distribution of left ventricular hypertrophy (59%) and marked septal thickening (mean 23 mm). In contrast, affected relatives were characterized by absence of functional limitation (72%) and subaortic obstruction (94%), localized and unusual sites of hypertrophy (60%) and only modest septal thickening (mean 17 mm).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiomyopathy, Hypertrophic↗

Microtia: a clinical and genetic study at the National Institute of Pediatrics in Mexico City.

BACKGROUND: Microtia is a malformation of the ear with extreme variability of expression. It is generally seen as an isolated malformation. However, some authors consider it to be a minimal manifestation of the oculo-auriculo-vertebral spectrum (OAVS), where, in addition, there are facial, vertebral, and renal abnormalities, among others. METHODS: A total of 145 pediatric patients with unilateral or bilateral microtia not considered as part of a syndrome were studied. All patients were subjected to an intentional clinical examination, a familial history, and radiographic imaging studies for ruling out associated malformations. Patients were classified into two groups: group 1 (60%), with isolated microtia; and group 2 (40%), considered as OAVS, with microtia associated with hemifacial skeletal microsomia, vertebral and/or renal malformations. RESULTS: No significant differences were found between the groups when the following variables were compared: gender; presence of unilateral or bilateral microtia; atretic external auditory canal; presence of preauricular tags; hearing loss of any type, and affection of the seventh cranial nerve, as well as associated malformations of other organs or systems. There were significant differences in relation to the presence of soft-tissue hemifacial microsomia, more frequently seen in patients with OAVS, because the majority of these patients had bone microsomia. Over 66% of the cases were sporadic and the rest were familiar. In 28.3% of the cases, the history suggested an autosomal-dominant inheritance pattern, and in 5.5%, an autosomal-recessive inheritance pattern, although in some familial cases, multifactorial inheritance could not be ignored. Some members in several families had isolated microtia, and others had mild characteristic manifestations of OAVS. CONCLUSIONS: Our results support the hypothesis that isolated microtia is a minimal expression of OAVS. Therefore, it is recommended that patients with microtia be subjected to intentional studies that search for malformations and physical examinations of first-degree relatives for adequate genetic counseling and management.

Adolescent↗

Plus-strand strong-stop DNA transfer in yeast Ty retrotransposons.

The yeast Ty1 LTR retrotransposon replicates by reverse transcription and integration; the process shows many similarities to the retroviral life cycle. However, we show that plus strand strong-stop DNA transfer in yeast Ty1 elements differs from the analogous retroviral process. By analysis of the native structure of the Ty1 primer binding site and by a series of manipulations of this region and assessment of the effects on retrotransposition, we show that primer binding site inheritance is not from the tRNA primer, which is inconsistent with classical retroviral models. This unusual inheritance pattern holds even when the Ty1 primer binding site is lengthened in order to be more retrovirus-like. Finally, the distantly related Ty3 element has an inheritance pattern like Ty1, indicating evolutionary conservation of the alternative pathway used by Ty1. Based on these results we arrive at a plus strand primer recycling model that explains Ty1 plus strand strong-stop DNA transfer and inheritance patterns in the primer binding site.

Binding Sites↗

Familial thoracic aortic aneurysms and dissections--incidence, modes of inheritance, and phenotypic patterns.

BACKGROUND: We examined the genetic nature and phenotypic features of thoracic aortic aneurysms (TAAs) and dissections in a large cohort of patients. METHODS: Interviews were conducted with 520 patients with TAAs and their pedigrees were compiled to identify family members with aneurysms. Study patients were divided into three groups: 101 non-Marfan patients, in 88 pedigrees, had a family pattern for TAA (familial group), 369 had no family pattern (sporadic group), and 50 had Marfan syndrome (MFS). We determined incidence of familial clustering, age at presentation, rate of aneurysm growth, incidence of hypertension, correlation of aneurysm sites among kindred, and pedigree inheritance patterns. RESULTS: An inherited pattern for TAA was present in 21.5% of non-MFS patients. The predominant inheritance pattern was autosomal dominant (76.9%), with varying degrees of penetrance and expressivity. The familial TAA group was significantly younger than the sporadic group (p < 0.0001), but not as young as the MFS group (p < 0.0001) (mean ages, 58.2 versus 65.7 versus 27.4 years). Among all 197 probands and kindred with aneurysm, 131 (66.5%) had TAA, 49 (24.9%) had abdominal aortic aneurysm (AAA), and 17 (8.6%) had cerebral or other aneurysms. Ascending aneurysm paired most commonly with ascending, and descending with abdominal. Abdominal aortic aneurysms (AAAs) and hypertension were more often associated with descending than with ascending TAAs (p < 0.001). Aortic growth rate was highest for the familial group (0.21 cm/y), intermediate for the sporadic group (0.16 cm/y), and lowest for the Marfan group (0.1 cm/y; p < 0.01). CONCLUSIONS: TAAs are frequently familial diseases. The predominant mode of inheritance is autosomal dominant. Familial TAAs have a relatively early age of onset. Aneurysms in relatives may be seen in the thoracic aorta, the abdominal aorta, or the cerebral circulation. Screening of first-order relatives of probands with TAA is essential. Familial TAAs tend to grow at a higher rate, exemplifying a more aggressive clinical entity.

Adult↗

The evolutionary processes of mitochondrial and chloroplast genomes differ from those of nuclear genomes.

This paper first introduces our present knowledge of the origin of mitochondria and chloroplasts, and the organization and inheritance patterns of their genomes, and then carries on to review the evolutionary processes influencing mitochondrial and chloroplast genomes. The differences in evolutionary phenomena between the nuclear and cytoplasmic genomes are highlighted. It is emphasized that varying inheritance patterns and copy numbers among different types of genomes, and the potential advantage achieved through the transfer of many cytoplasmic genes to the nucleus, have important implications for the evolution of nuclear, mitochondrial and chloroplast genomes. Cytoplasmic genes transferred to the nucleus have joined the more strictly controlled genetic system of the nuclear genome, including also sexual recombination, while genes retained within the cytoplasmic organelles can be involved in selection and drift processes both within and among individuals. Within-individual processes can be either intra- or intercellular. In the case of heteroplasmy, which is attributed to mutations or biparental inheritance, within-individual selection on cytoplasmic DNA may provide a mechanism by which the organism can adapt rapidly. The inheritance of cytoplasmic genomes is not universally maternal. The presence of a range of inheritance patterns indicates that different strategies have been adopted by different organisms. On the other hand, the variability occasionally observed in the inheritance mechanisms of cytoplasmic genomes reduces heritability and increases environmental components in phenotypic features and, consequently, decreases the potential for adaptive evolution.

Animals↗

Unusual pattern of inheritance and orodental changes in the Ellis-van Creveld syndrome.

Ellis-van Creveld (EVC) syndrome (chondroectodermal dysplasia, mesoectodermal dysplasia, OMIM 225500) is an autosomal recessive skeletal dysplasia characterized by short limbs, short ribs, postaxial polydactyly and dysplastic nails and teeth. Oral manifestations tend to be pathognomonic such as multiple broad labial frenula and congenital missing teeth. In this study we report three Egyptian families with six cases of EVC syndrome. An unusual pattern of inheritance with father to son or to daughter transmission was observed in 2 consanguineous families thus demonstrating pseudo-dominant inheritance, probably for the first time in the literature. A new consistent orodental anomaly found in all our cases was bifid tip of the tongue. We emphasize study of orodental anomalies in future cases for accurate diagnosis of Ellis-van Creveld syndrome and its probable differential diagnosis from Weyers acrodental dysostosis.

Adolescent↗

Familial subarachnoid hemorrhage: distinctive features and patterns of inheritance.

To delineate the distinctive features of familial subarachnoid hemorrhage, we compared gender and age at the time of subarachnoid hemorrhage, as well as site and number of aneurysms, in patients with familial subarachnoid hemorrhage (at least 1 first-degree relative with subarachnoid hemorrhage) and patients with sporadic subarachnoid hemorrhage (no subarachnoid hemorrhage in first- or second-degree relatives), in a prospective, hospital-based series of patients. In addition we studied the pattern of inheritance in 17 families with familial subarachnoid hemorrhage. Mean age at the time of hemorrhage in patients with the familial form was 6.8 years lower than that in those with the sporadic form, and middle cerebral artery aneurysms occurred more often in patients with familial disease. Sex distribution and number of aneurysms were similar in the two groups. Inheritance was compatible with autosomal dominant transmission in some families, and with autosomal recessive or multifactorial transmission in others. In our 5 families as well as in all 18 previously reported families with two affected generations, the age at the time of subarachnoid hemorrhage was invariably lower in later generations, which is suggestive of anticipation. We conclude that familial subarachnoid hemorrhage is a separate entity with occurrence at a young age, predilection for aneurysms of the middle cerebral artery, and variable modes of inheritance, including autosomal dominant inheritance with possible anticipation.

Adult↗