Genomewide homozygosity mapping and molecular analysis of a candidate gene located on 22q13 (fibulin-1) in a previously undescribed vitreoretinal dystrophy

OBJECTIVES To localize the gene that causes an autosomal recessively inherited vitreoretinal dystrophy that has not been described, to our knowledge, and to analyze a candidate gene mapped to 22q13 (fibulin-1 [FBLN1]). METHODS Homozygosity mapping with 500 microsatellite markers spread over the whole genome (mean distance, 7.2 centimorgans [cM]) and mutation analysis of the complete coding region of FBLN1. RESULTS Homozygosity for all analyzed markers was found in the 4 affected siblings in a region on chromosome 22 encompassing 12 cM from D22S444 (centromeric) to D22S1170 (telomeric). Lod scores were between 0.017 and 2.36 (theta = 0). A mutation analysis of the complete coding region of FBLN1, which encodes interacting extracellular matrix proteins, revealed 4 previously undescribed single nucleotide polymorphisms. CONCLUSIONS A genomewide homozygosity mapping analysis supported the hypothesis that the gene responsible for a unique vitreoretinal dystrophy is located on chromosome 22q13. No obviously pathogenic mutation was found in the candidate gene, FBLN1

Uniparental disomy 7 in Silver—Russell syndrome and primordial growth retardation

Maternal uniparental disomy for the entire chromosome 7 has so far been reported in three patients with intrauterine and postnatal growth retardation. Two were detected because they were homozygous for a cystic fibrosis mutation for which only the mother was heterozygous, and one because he was homozygous for a rare COL1A2 mutation. We investigated 35 patients with either the Silver-Russell syndrome or primordial growth retardation and their parents with PCR markers to search for uniparental disomy 7. Four of 35 patients were found to have maternal disomy, including three with isodisomy and one with heterodisomy. The data confirm the hypothetical localization of a maternally imprinted gene (or more than one such gene) on chromosome 7. It is suggested to search for UPD 7 in families with an offspring with sporadic Silver-Russell syndrome or primordial growth retardatio

<資料>新西蘭,加奈陀,印度の中央銀行設立計畫

<p><b>Panels A–C,</b> representative images obtained from confocal microscopy of transiently transfected HEK cells. R835Q mutant channels do not appear differently distributed in comparison to WT KCNH2. <b>D</b>, Immunoblots using anti-erg1 (2, 5 µg/mL) of crude membrane extracts from heterologous expression in HEK cells, indicating equal protein expression level. Illustrated below are endoplasmic reticulum and plasma membrane fraction with respective markers of equal protein loading (calnexin for endoplasmic reticulum, spectrin for plasma membranes). Exemplary Western blots of preparations at physiological temperature (37°C) and 40°C (to simulate febrile illness of the index patient’s brother) are shown. No differences were observed in Kv11.1-WT or Kv11.1-R835Q plasma membrane representation of the two proteins under the two conditions. ER: endoplasmic reticulum fraction; PM: plasma-membrane fraction; WT: wild type; NT: non-transfected cells.</p

Abnormal phenotypes in uniparental disomy (UPD): fundamental aspects and a critical review with bibliography of UPD other than 15

Uniparental disomy (UPD) is the inheritance of both homologous chromosomes from only one parent. The bases are always two events, either two meiotic, or one meiotic and one mitotic, or two mitotic. An aberrant imprint, homozygosity of autosomal recessive gene mutations, homozygosity of X-chromosomal disorders in females, and father-to-son transmission of X-linked traits are the possible and yet repeatedly documented consequences sometimes associated with unfavorable handicaps. Fertilization of a disomic (=hyperhaploid) gamete by a gamete monosomic for the same chromosome and subsequent loss of the normally inherited chromosome (trisomy rescue) is the most frequently supposed mechanism of formation and might result in mosaicism in the placenta or even in a subset of fetal tissues. This low-level mosaicism can remain undetected and renders the delineation of a phenotype more difficult. Therefore, the phenotype of cases with UPD is determined by mosaicism, genomic imprinting, the nonmendelian inheritance of monogenic disorders, or by a combination of all these factors. A survey of all reported cases demonstrates a preponderance of maternal versus paternal UPD (approximately 3:1) and an unequal chromosomal distribution. Most likely, deleterious trisomy mosaicism, imprinted genes, the nature of the chromosome itself, the clinical interest in a single chromosome, and, last but not least, an ascertainment bias are therefore responsible

Paternal meiotic origin of der(21;21)(q10;q10) mosaicism [46,XX/46,XX,der(21;21)(q10;q10),+21] in a girl with mild Down syndrome

Mosaicism for a derivative 21, der(21;21)(q10;q10), is a rare chromosomal abnormality. Since a normal cell line is present, mitotic origin is considered. Chromosome examination of a female with developmental delay and dysmorphic features compatible with mosaic trisomy 21 revealed a normal cell line and a second cell line with a der(21;21)(q10;q10) [46,XX/46,XX,der(21;21)(q10;q10),+21]. Molecular investigation with a panel of highly polymorphic microsatellites mapping to chromosome 21 demonstrated three different alleles, two of paternal and one of maternal origin. Therefore, either formation of the der(21;21)(q10;q10) during paternal meiosis with subsequent loss of the der(21;21)(q10;q10) and mitotic reduplication of the maternal homologue in the normal cell line, or more likely a zygote with paternally derived trisomy 21 and subsequent mitotic formation of the der(21;21)(q10;q10) have to be considered. This case again shows that mammalian chromosome aberrations may have a more complex mechanism of formation than was previously thought

Marden-Walker syndrome in an adult

We report on a 23-year-old male with growth retardation, blepharophimosis, congenital contractures, minor anomalies of the face, and severe mental retardation. This patient is the second adult reported with the Marden-Walker syndrome. Blepharophimosis, contractures, growth retardation, and developmental delay persisted whereas minor anomalies of the face were less noticeable as the patient grew older. Behaviour changed from kindness in childhood to restlessness, hyperactivity and aggressiveness in adolescence

Maternal uniparental isodisomy 11q13right-arrowqter in a dysmorphic and mentally retarded female with partial trisomy mosaicism 11q13right-arrowqter

EDITOR—Partial trisomy mosaicism describes the presence of a normal cell line together with an unbalanced translocation in a second cell line. Its incidence is not known. Only a few cases have been published,1 almost all with developmental delay and a pattern of dysmorphism. The presence of a normal cell line points towards postzygotic formation, but the origin and mechanism of formation have so far only been investigated in one case of partial trisomy 16p mosaicism and in another case of partial trisomy 21q mosaicism.2 3 In the former, a complex formation by trisomy first, translocation second, and uniparental disomy and partial trisomy third was inferred. In the latter, paternal meiotic origin of der(21;21)(q10;q10) mosaicism (46,XX/46,XX,der(21;21)(q10;q10),+21) in a girl with mild Down syndrome was described. Here, we report on a 25 year old woman with mental retardation, dysmorphic features, partial trisomy 11q13→qter mosaicism (46,XX, der(19)t(11;19)(q13;p13.3)/46,XX), maternal uniparental isodisomy 11q13→qter in the normal cell line, and two maternal and one paternal segment(s) 11q13→qter in the abnrmal cell line

Escher-Hirt syndrome

A mother and her two daughters are reported with bilateral conductive deafness due to incudo-stapedial abnormalities, and microtia with thickened ear lobes. This pattern of abnormal findings, transmitted with an autosomal dominant mode of inheritance, is characteristic of the Escher-Hirt syndrome. One of the daughters died from an additional cardiac malformation (VSD). Anomalies of the middle ear were demonstrated in the surviving patients by computed tomography. Differential diagnosis with other genetic syndromes associated with deafness, and possible therapeutic approaches are discussed

Iron supplementation associated with loss of phenotype in autosomal dominant hypophosphatemic rickets

Context: Autosomal dominant hypophosphatemic rickets (ADHR) is the only hereditary disorder of renal phosphate wasting in which patients may regain the ability to conserve phosphate. Low iron status plays a role in the pathophysiology of ADHR. Objective: This study reports of a girl with ADHR, iron deficiency, and a paternal history of hypophosphatemic rickets that resolved without treatment. The girl's biochemical phenotype resolved with iron supplementation. Subjects: A 26-month-old girl presented with typical features of hypophosphatemic rickets, short stature (79 cm; −2.82 SDS), and iron deficiency. Treatment with elemental phosphorus and calcitriol improved her biochemical profile and resolved the rickets. The girl's father had presented with rickets at age 11 months but never received medication. His final height was reduced (154.3 cm; −3.51 SDS), he had undergone corrective leg surgery and had an adult normal phosphate, fibroblast growth factor 23, and iron status. Father and daughter were found to have a heterozygous mutation in exon 3 of the FGF23 gene (c.536G&amp;gt;A, p.Arg179Gln), confirming ADHR. Intervention: Withdrawal of rickets medication was attempted off and on iron supplementation. Results: Withdrawal of rickets medication in the girl was unsuccessful in the presence of low-normal serum iron levels at age 5.6 years but was later successful in the presence of high-normal serum iron levels following high-dose iron supplementation. Conclusions: We report an association between iron supplementation and a complete loss of biochemical ADHR phenotype, allowing withdrawal of rickets medication. Experience from this case suggests that reduction and withdrawal of rickets medication should be attempted only after iron status has been optimized. </jats:sec