RESUMO
PURPOSE: We observed four individuals in two unrelated but consanguineous families from Portugal and Brazil affected by early-onset retinal degeneration, sensorineural hearing loss, microcephaly, intellectual disability, and skeletal dysplasia with scoliosis and short stature. The phenotype precisely matched that of an individual of Azorean descent published in 1986 by Liberfarb and coworkers. METHODS: Patients underwent specialized clinical examinations (including ophthalmological, audiological, orthopedic, radiological, and developmental assessment). Exome and targeted sequencing was performed on selected individuals. Minigene constructs were assessed by quantitative polymerase chain reaction (qPCR) and Sanger sequencing. RESULTS: Affected individuals shared a 3.36-Mb region of autozygosity on chromosome 22q12.2, including a 10-bp deletion (NM_014338.3:c.904-12_904-3delCTATCACCAC), immediately upstream of the last exon of the PISD (phosphatidylserine decarboxylase) gene. Sequencing of PISD from paraffin-embedded tissue from the 1986 case revealed the identical homozygous variant. In HEK293T cells, this variant led to aberrant splicing of PISD transcripts. CONCLUSION: We have identified the genetic etiology of the Liberfarb syndrome, affecting brain, eye, ear, bone, and connective tissue. Our work documents the migration of a rare Portuguese founder variant to two continents and highlights the link between phospholipid metabolism and bone formation, sensory defects, and cerebral development, while raising the possibility of therapeutic phospholipid replacement.
Assuntos
Carboxiliases/genética , Carboxiliases/metabolismo , Adolescente , Adulto , Brasil , Exoma/genética , Feminino , Genótipo , Células HEK293 , Perda Auditiva Neurossensorial/genética , Humanos , Deficiência Intelectual/genética , Masculino , Microcefalia/genética , Anormalidades Musculoesqueléticas/genética , Osteocondrodisplasias/genética , Linhagem , Fenótipo , Portugal , Degeneração Retiniana/genética , Síndrome , Adulto JovemRESUMO
BACKGROUND: Histologic delineation of the events involved in the development of long bones and the developmental age at which these events occur is needed to elucidate the genetic and molecular mechanisms associated with these events. This report describes the sequence of histologic events involved in the formation of long bones and their epiphyses in the New Zealand White rabbit. METHODS: Prenatal studies were performed on twelve, fourteen, fifteen, sixteen, eighteen, twenty-one, twenty-four, and twenty-seven-day-old rabbit embryos, and postnatal studies were performed on newborn rabbits and on three-to-four-day-old; one, two, four, and six-week-old; and two, three, four, six, and eight-month-old rabbits. Histologic specimens from embryos were embedded in plastic and stained with toluidine blue or safranin O-fast green, and specimens from postnatal rabbits were embedded in paraffin and stained with hematoxylin and eosin or safranin O-fast green. RESULTS: Studies of twelve-day-old embryos demonstrated upper and lower limb buds filled with undifferentiated mesenchymal cells, and studies of fourteen-day-old embryos showed mesenchymal condensation and beginning cartilage formation outlining major long bones. Long-bone and epiphyseal development progressed through sixteen structural stages, and the developmental age at which these stages occurred was determined. These stages included limb-bud formation with uniform distribution of mesenchymal cells and formation of an apical ectodermal ridge (stage 1); mesenchymal condensation (stage 2); cartilage differentiation (stage 3); formation of a primary center of ossification (stage 4a); epiphyseal cartilage vascularization with formation of cartilage canals (stage 7); vascular invasion of the developing secondary ossification center (stage 9); bone formation and marrow cavitation in the secondary ossification center with formation of hematopoietic marrow (stage 10); fullest relative extent of secondary-ossification-center development in epiphyseal cartilage (stage 14); thinning of the physis (stage 15); and resorption of the physis with establishment of continuity between epiphyseal and metaphyseal circulations (stage 16).