Prenatal sonographic diagnosis of diastrophic dwarfism

A healthy 27-year-old pregnant woman underwent sonographic examination because her uterine size was large for 20 weeks' menstrual age. Sonograms showed short fetal limbs with hitchhiker thumbs and toes, thoracic scoliosis, clubbed feet, and polyhydramnios. The ossification of all bony structures appeared normal, and there was no evidence of fractures. On the basis of these sonographic findings, we diagnosed skeletal dysplasia and short-limbed dwarfism, most likely diastrophic dwarfism. We counseled the parents, and the pregnancy was continued. At 37 weeks menstrual age, the patient vaginally delivered a male infant that weighed 2,560 g. The infant survived with respiratory support during his first few days of life. Postnatal physical and radiologic examinations confirmed the prenatal diagnosis of diastrophic dwarfism. Sonography is the modality of choice for prenatal detection of diastrophic dwarfism.

Indian hedgehog coordinates endochondral bone growth and morphogenesis via parathyroid hormone related-protein-dependent and -independent pathways

Indian hedgehog (Ihh) and Parathyroid Hormone-related Protein (PTHrP) play a critical role in the morphogenesis of the vertebrate skeleton. Targeted deletion of Ihh results in short-limbed dwarfism, with decreased chondrocyte proliferation and extensive hypertrophy, features shared by mutants in PTHrP and its receptor. Activation of Ihh signaling upregulates PTHrP at the articular surface and prevents chondrocyte hypertrophy in wild-type but not PTHrP null explants, suggesting that Ihh acts through PTHrP. To investigate the relationship between these factors during development of the appendicular skeleton, mice were produced with various combinations of an Ihh null mutation (Ihh(−/−)), a PTHrP null mutation (PTHrP(−/−)), and a constitutively active PTHrP/Parathyroid hormone Receptor expressed under the control of the Collagen II promoter (PTHrPR*). PTHrPR* rescues PTHrP(−/−) embryos, demonstrating this construct can completely compensate for PTHrP signalling. At 18.5 dpc, limb skeletons of Ihh, PTHrP compound mutants were identical to Ihh single mutants suggesting Ihh is necessary for PTHrP function. Expression of PTHrPR* in chondrocytes of Ihh(−/−) mice prevented premature chondrocyte hypertrophy but did not rescue either the short-limbed dwarfism or decreased chondrocyte proliferation. These experiments demonstrate that the molecular mechanism that prevents chondrocyte hypertrophy is distinct from that which drives proliferation. Ihh positively regulates PTHrP, which is sufficient to prevent chondrocyte hypertrophy and maintain a normal domain of cells competent to undergo proliferation. In contrast, Ihh is necessary for normal chondrocyte proliferation in a pathway that can not be rescued by PTHrP signaling. This identifies Ihh as a coordinator of skeletal growth and morphogenesis, and refines the role of PTHrP in mediating a subset of Ihh's actions.

Clinical and roentgenographic findings in a patient with primordial microcephalic dwarfism type Caroline Crachami

We describe a patient with primordial microcephalic dwarfism with severe intrauterine growth retardation and severe and progressive postnatal deficit in length, weight and head circumference. The patient was extroverted and sociable but mildly mentally retarded. He had marked delay of bone maturation and an enlargement of the sella turcica. This child and two previously reported patients [Boscherini et al., Eur J Pediatr 137:237-242, 1981] have many characteristics in common with Caroline Crachami, the famous "Sicilian dwarf". We think that these patients belong to a separate category of microcephalic primordial dwarfism.

Anterior pituitary cells defective in the cell-autonomous factor, df, undergo cell lineage specification but not expansion

The Ames dwarf mouse transmits a recessive mutation (df) resulting in a profound anterior pituitary hypocellularity due to a general lack of thyrotropes, somatotropes and lactotropes. These cell types are also dependent on the pituitary-specific transcription factor, Pit-1. We present evidence that expression of Pit-1 and limited commitment to these cells lineages occurs in df/df pituitaries. Thus, the crucial role of df may be in lineage-specific proliferation, rather than cytodifferentiation. The presence of all three Pit-1-dependent cell types in clonally derived clusters provides compelling evidence that these three lineages share a common, pluripotent precursor cell. Clusters containing different combinations of Pit-1-dependent cell types suggests that the Pit-1+ precursor cells choose from multiple developmental options during ontogeny. Characterization of df/df<-->+/+ chimeric mice demonstrated that df functions by a cell-autonomous mechanism. Therefore, df and Pit-1 are both cell-autonomous factors required for thyrotrope, somatotrope and lactotrope ontogeny, but their relative roles are different.

Embryonic death, dwarfism and fetal malformations after irradiation of embryos at the zygote stage: studies on two mouse strains

Female mice of the BALB/c and CF1 strains were mated and irradiated with various doses of X-rays 7 h after presumed fertilization. 18 days later, females were killed and their uteri examined for prenatal mortality at the different stages of development. Living fetuses were weighed and examined for the presence of external malformations. A number of them were also examined for skeletal anomalies. Radiation induced mainly a dose-dependent increase of the preimplantation loss in the BALB/c strain and of the early postimplantation loss in the CF1 strain. Embryos of the BALB/c strain were refractory to the induction of teratogenic effects after such preimplantation irradiation. In CF1 mice, the frequency of malformed fetuses increased regularly after irradiation, the difference with controls being significant for the doses of 10, 50 and 100 cGy. Dwarfism occurrence also appeared to be increased by irradiation in this strain, although the importance of this effect varied depending on the criterion chosen for the assessment of dwarfs. With the definition proposed in the present paper, the increase in the frequency of dwarfs paralleled that of malformed fetuses, being significant after doses of 50 and 100 cGy. Irradiation did not increase the frequency of skeletal anomalies. A careful examination of the various data obtained to data led us to conclude that radiation may possibly be teratogenic in several mouse strains, when administered as early as during the one-cell stage and, to a lesser extent, during the following preimplantation stages. However, early prenatal mortality will remain by far the greatest risk associated with an exposure to radiation during this period. Moreover, the relativity of the risk of abnormality due to such irradiation should be considered in the context of the high prevalence of developmental defects spontaneously occurring during human pregnancy.

Geleophysic dysplasia: a report of three affected boys--prenatal ultrasound does not detect recurrence

Geleophysic dysplasia is characterized by short stature with short limbs and brachydactyly, a "happy" facial appearance, and joint contractures. Infiltration of heart valves and liver with a mucopolysaccharide-like substance has been demonstrated in some patients. A metabolic pathogenesis is suspected, but has not yet been identified. We report on 3 boys with the condition, 2 of whom are brothers. Serial ultrasound scans were performed on 2 of the cases during pregnancy, but short limbs did not become obvious until after 28 weeks of gestation, making it an uninformative procedure for prenatal diagnosis.

Prenatal diagnosis of metatropic dwarfism

We present a case of prenatal diagnosis of severe metatropic dysplasia at 20 weeks' gestation. The characteristic prenatal features of this rare autosomal recessive chondrodysplasia appear to be significant dwarfism with an enlarged head and a narrow thorax associated with enlargement of the hands and feet, and the radiographic 'dumb-bell' appearance of the long bones.

Early prenatal diagnosis of polycystic pancreas with narrow thorax and short limb dwarfism

We describe the ultrasound findings of polycystic pancreas with short rib dwarfism in the early second trimester. Radiologic, morphologic, and histologic examination after pregnancy termination confirmed the findings and also disclosed dysplastic kidneys. The skeletal anomalies are similar to those in Verma Naumoff type of short rib polydactyly, but the extraskeletal malformations have never been reported before in this syndrome.

Failure to make normal alpha ryanodine receptor is an early event associated with the crooked neck dwarf (cn) mutation in chicken

We have investigated the molecular basis of the Crooked Neck Dwarf (cn) mutation in embryonic chickens. Using biochemical and pharmacological techniques we are unable to detect normal alpha ryanodine receptor (RyR) protein in intact cn/cn skeletal muscle. Extremely low levels of alpha RyR immunoreactivity can be observed in mutant muscles, but the distribution of this staining differs from that in normal muscle and colocalizes with the rough endoplasmic reticulum immunoglobulin binding protein, BiP. This suggests the existence of an abnormal alpha RyR protein in mutant muscle. In day E12 cn/cn muscle the levels of RyR mRNA are reduced by approximately 80%, while the levels of other muscle proteins, including the alpha 1 subunit of the dihydropyridine receptor, the SR Ca(2+)-ATPase, calsequestrin, and glyceraldehyde-3-phosphate dehydrogenase, and their associated mRNAs are essentially normal in cn/cn muscle. There is also a failure to express alpha RyR in cn/cn cerebellar Purkinje neurons. Expression of the beta RyR, a second RyR isoform, is not initiated in normal skeletal muscle until day E18. In cn/cn skeletal muscle significant muscle degeneration has occurred by this time and the beta RyR is found at low levels in only a subset of fibers suggesting the reduced levels of this isoform are a secondary consequence of the mutation. The cardiac RyR isoform is found in cn/cn cardiac muscle, which contracts in a vigorous manner. In summary, a failure to make normal alpha RyR receptor appears to be an event closely associated with the cn mutation and one which may be largely responsible for development of the cn/cn phenotype in embryonic skeletal muscle.

Crooked neck dwarf (cn) mutant chicken skeletal muscle cells in low density primary cultures fail to express normal alpha ryanodine receptor and exhibit a partial mutant phenotype

The Crooked Neck Dwarf (cn) mutation in chickens causes marked changes in intact embryonic skeletal muscle. We have investigated whether the cn/cn phenotype develops in vitro, and if cultured muscle cells are suitable for studies of this mutation. The properties of cn/cn muscle cells maintained in low density primary cultures (6.25 x 10(3) cells/cm2) are described in this report. In normal muscle cells, the alpha ryanodine receptor (RyR) isoform appears prior to, and at greater levels than, the beta RyR, and is detected in mononucleated myocytes. The beta RyR isoform appears within 24 hr after the initiation of myotube formation, which is earlier than anticipated from studies with intact embryonic muscle. Normal alpha RyR protein is not detected in cultured cn/cn muscle cells, whereas the beta RyR, the alpha 1-subunit of the dihydropyridine receptor, the sarcoplasmic reticulum Ca(2+)-ATPase, and calsequestrin are expressed at comparable levels in normal and mutant muscle cells. Calcium transients elicited by electrical stimulation, acetylcholine, and caffeine are similar in normal and cn/cn cultured myotubes and are blocked by ryanodine in both cell types. In addition, comparable L- and T-type calcium currents are observed in normal and mutant muscle cells, suggesting that both the alpha 1-subunit of the dihydropyridine receptor and the beta RyR in mutant muscle cells are functional. Normal and cn/cn muscle cells proliferate and form myotubes in a similar manner. These latter events do not appear to depend on sarcoplasmic reticulum calcium release, as they also occur in normal muscle cells in which calcium release is prevented by chronic treatment with 100 microM ryanodine. Both cn/cn and ryanodine-treated normal muscle cells exhibit morphological changes similar to those observed in intact cn/cn skeletal muscle. Thus, the mutant phenotype observed in ovo is partially expressed under low density culture conditions, and neither beta RyR protein nor its function appear to be capable of preventing the associated changes.

The cartilage proteoglycan deficient mutation, nanomelia, contains a DNA polymorphism in the proteoglycan core protein gene that is genetically linked to the nanomelia phenotype

The avian mutation, nanomelia (nm), is an autosomal recessive embryonic lethal. Homozygous embryos show hypoplasia of the limbs and a parrot-like beak. Biochemical studies have associated this phenotype with the absence of the major cartilage specific proteoglycan core protein (Argraves et al., 1981). Stirpe et al. (1987) demonstrated a reduction in core protein transcripts in nanomelic embryos. Southern analyses did not detect a rearrangement of the core protein gene or a restriction fragment length polymorphism (RFLP) in the core protein gene linked to the nanomelia mutation. These data suggest that the genetic lesion associated with the nanomelia mutation is either a subtle alteration in the core protein gene affecting the biosynthesis of core protein transcript or a defect in a regulatory gene that produces a trans-acting factor requisite for the proper expression of the core protein gene. To distinguish between these two alternative molecular mechanisms for the nanomelia mutation, experiments were conducted to demonstrate genetic linkage or non-linkage of the core protein gene to the nanomelia mutation. Using denaturing gradient gel electrophoresis (DGGE) technology, a DNA polymorphism has been identified at the 3' end of the core protein gene. The polymorphism defines two alleles, one allele is associated with the normal core protein gene, while the other allele always segregates with the nanomelia mutation. These results suggest that the identified DNA polymorphism in the core protein gene is genetically linked to the inheritance of the nanomelic phenotype and the nanomelia mutation contains a lesion in the core protein gene.

A new autosomal recessive lethal chondrodystrophy with congenital hydrops

Two sibs, the offspring of consanguineous parents, presented with severe short-limb dwarfism and distinct chondro-osseous, radiologic, and histologic appearance. The first sib presented at 30 wk with severe hydrops following fetal death; the second was detected by ultrasonography at 20 wk. Radiologic abnormalities included an unusual "moth-eaten" appearance of the markedly short long bones, bizzare ectopic ossification centers, and marked platyspondyly with unusual ossification centers. Marked extramedullary erythropoiesis was present in both fetuses, and chondro-osseous histology was characterized by marked disorganization of tissue with interspersed masses of cartilage, bone, and mesenchymal tissue. These sibs appear to have a distinct previously unreported autosomal recessive skeletal dysplasia, which can present as hydrops fetalis.

Fine structure of pituitary blood vessels in embryos of the dwarf (dw) mutant mouse

Blood vessels in the pars distalis of the embryonic pituitary gland of the dwarf (dw) mutant mouse were analyzed by means of electron microscopy. Dwarf (dw/dw) embryos ranging in age from 15 through 18 days of gestation were obtained from matings of dwarf homozygotes in which reproductivity was induced by means of hormone supplementation and grafts of normal pituitary to the kidney capsule. Endothelial cells in vessels of the dwarf pituitary were retarded in development as indicated by a retention of macrovesicles and marginal flaps beyond embryonic stages when they normally subside in normal embryos, as well as a lag in the development of endothelial cell attenuations. This retardation may be causally related to the pituitary pathology involving faulty cytodifferentiation of somatotrophs and mammotrophs.

Accelerated maturation of limb mesenchyme by the BrachypodH mouse mutation

Mesenchyme cell populations prepared from proximal and distal halves of stage 20 mouse forelimb buds are shown to behave under in vitro micromass culture conditions like analogous cell populations obtained from chick embryo limb buds. While the distal cells are spontaneously chondrogenic, the proximal cells make aggregates which are only potentially chondrogenic after treatment with dibutyryl cyclic AMP. In addition, stage 20 mouse whole limb bud cells homozygous for the brachypodismH (bpH) mutation are shown to behave similarly to 'normal' proximal cells. Both make fewer aggregates and nodules and both have faster aggregation rates (determined as the rate of disappearance of single cells over time) in rotation cultures than 'normal' distal or whole limb bud cells. These results support the hypothesis that the bpH mutation specifically decreases the proportion of spontaneously chondrogenic mesenchyme cells (that is, distal-like cells) present at certain developmental stages in the limb bud, resulting in a prematurely high proportion of proximal-like cells.

Disproportionate micromelia (Dmm): an incomplete dominant mouse dwarfism with abnormal cartilage matrix

This paper describes a new autosomal incomplete dominant dwarfism, disproportionate micromelia, which has been characterized genetically and phenotypically, and the cartilage of homozygotes, and heterozygotes has been examined by histochemical, immunofluorescence and biochemical methods. Homozygotes, which die at birth, are disproportionately short and have cleft palates. The heterozygotes appear normal at birth but beginning at 1 week of age dwarfism is apparent and increases during growth. Histochemical and biochemical analyses of the cartilage rudiments of homozygotes at day 18 of gestation demonstrate that the cartilage growth plate is disorganized and the matrix components, collagen and proteoglycan, are altered. Total collagen synthesis is reduced by approximately 30% and the amount of type II collagen is greatly reduced. By immunofluorescence staining with collagen antibodies, it appears that type II collagen is located primarily near the cell surface of chondrocytes but is poorly distributed throughout the remainder of the matrix. The amount of proteoglycan in the cartilage matrix is reduced by approximately 70% as determined by chemical analysis of hexosamines and by [35S]sulfate incorporation. Although the proteoglycans synthesized by the mutant are normal in size and in glycosaminoglycan composition, they were more easily extractable from the matrix than were normal cartilage proteoglycans. Heterozygotes had reduced cartilage matrix proteoglycan by histochemical methods, but the organization of the epiphyseal cartilage was not abnormal. These data suggest that a reduced or abnormal cartilage matrix is the cause of the dwarfism.

Short-limbed dwarfism: ultrasonographic diagnosis by mensuration of fetal femoral length

The femoral lengths of 70 normal fetuses, five short-limbed dwarfs, and two additional normal fetuses at risk for dwarfism were measured employing linear array real-time (rapid B-scan) ultrasonographic systems. Early results indicate that prenatal diagnosis of short-limbed dwarfs can be accomplished by this technique, in some instances early enough to allow parents to consider elective abortion. The data also indicate fundamental differences in the growth pattern of certain dwarf syndromes.

Achondrogenesis, type I

Achondrogenesis is a rare form of lethal dwarfism. Usually discovered post partum, in a few instances only it has been diagnosed in utero. One such a case is here presented together with differential diagnosis with other forms of lethal dwarfism.