Recurrent tetraamelia and pulmonary hypoplasia with multiple malformations in sibs

A 50-kb deletion disrupting the RSPO2 gene is associated with tetradysmelia in Holstein Friesian cattle

Background

Tetradysmelia is a rare genetic disorder that is characterized by an extremely severe reduction of all limb parts distal of the scapula and pelvic girdle. We studied a Holstein Friesian backcross family with 24 offspring, among which six calves displayed autosomal recessive tetradysmelia. In order to identify the genetic basis of the disorder, we genotyped three affected calves, five dams and nine unaffected siblings using a Bovine Illumina 50 k BeadChip and sequenced the whole genome of the sire.

Results

Pathological examination of four tetradysmelia cases revealed a uniform and severe dysmelia of all limbs. Applying a homozygosity mapping approach, we identified a homozygous region of 10.54 Mb on chromosome 14 (Bos taurus BTA14). Only calves that were diagnosed with tetradysmelia shared a distinct homozygous haplotype for this region. We sequenced the whole genome of the cases’ sire and searched for heterozygous single nucleotide polymorphisms (SNPs) and small variants on BTA14 that were uniquely present in the sire and absent from 3102 control whole-genome sequences of the 1000 Bull Genomes Project, but none were identified in the 10.54-Mb candidate region on BTA14. Therefore, we subsequently performed a more comprehensive analysis by also considering structural variants and detected a 50-kb deletion in the targeted chromosomal region that was in the heterozygous state in the cases’ sire. Using PCR, we confirmed that this detected deletion segregated perfectly within the family with tetradysmelia. The deletion spanned three exons of the bovine R-spondin 2 (RSPO2) gene, which encode three domains of the respective protein. R-spondin 2 is a secreted ligand of leucine-rich repeats containing G protein-coupled receptors that enhance Wnt signalling and is involved in a broad range of developmental processes during embryogenesis.

Conclusions

We identified a 50-kb deletion on BTA14 that disrupts the coding sequence of the RSPO2 gene and is associated with bovine tetradysmelia. To our knowledge, this is the first reported candidate causal mutation for tetradysmelia in a large animal model. Since signalling pathways involved in limb development are conserved across species, the observed inherited defect may serve as a model to further elucidate fundamental pathways of limb development.

Amelia-meromelia sequence with atrial septal defect-a rare occurrence

Amelia and Meromelia may either present as an isolated defect or associated with other malformations; and the diagnosis is mainly clinical. The antenatal period of the case presented here was medically unsupervised but uneventful. The baby had bilateral upper limb Meromelia and bilateral lower limb Amelia along with a small ostium secundum atrial septal defect. Except for the young age of mother, there was no other obvious risk factor in this case. The baby had a normal and healthy neonatal outcome whereas most such cases are either stillborn or end in early neonatal death.

A review of supernumerary and absent limbs and digits of the upper limb

For years people have been enamored by anomalies of the human limbs, particularly supernumerary and absent limbs and digits. Historically, there are a number of examples of such anomalies, including royal families of ancient Chaldea, tribes from Arabia, and examples from across nineteenth century Europe. The development of the upper limbs in a growing embryo is still being elucidated with the recent advent of homeobox genes, but researchers agree that upper limbs develop between stages 12-23 through a complex embryological process. Maternal thalidomide intake during limb development is known to cause limb reduction and subsequent amelia or phocomelia. Additionally, a number of clinical reports have illustrated different limb anomaly cases, with each situation unique in phenotype and developmental abnormality. Supernumerary and absent limbs and digits are not unique to humans, and a number of animal cases have also been reported. This review of the literature illustrates the historical, anatomical, and clinical aspects of supernumerary and absent limbs and digits for the upper limb.

Tetra-amelia with lung hypoplasia and facial clefts, Roberts-SC syndrome: report of two cases

Although limb anomalies are a common clinical problem, they are rarely studied. The spectrum of limb anomalies ranges from very mild disorders such as syndactyly to very severe forms such as absent limb (amelia). Tetra-amelia is a rare anomaly with complete or partial deficiency of all four limbs. It may be isolated or associated with other anomalies. Roberts-SC phocomelia syndrome comprises four limb deficiencies, lung hypoplasia, facial clefts and other anomalies. We describe two cases that presented to us.

Homozygous WNT3 mutation causes tetra-amelia in a large consanguineous family

Tetra-amelia is a rare human genetic disorder characterized by complete absence of all four limbs and other anomalies. We studied a consanguineous family with four affected fetuses displaying autosomal recessive tetra-amelia and craniofacial and urogenital defects. By homozygosity mapping, the disease locus was assigned to chromosome 17q21, with a maximum multipoint LOD score of 2.9 at markers D17S931, D17S1785, D17SS1827, and D17S1868. Further fine mapping defined a critical interval of approximately 8.9 Mb between D17S1299 and D17S797. We identified a homozygous nonsense mutation (Q83X) in the WNT3 gene in affected fetuses of the family. WNT3, a human homologue of the Drosophila wingless gene, encodes a member of the WNT family known to play key roles in embryonic development. The Q83X mutation truncates WNT3 at its amino terminus, suggesting that loss of function is the most likely cause of the disorder. Our findings contrast with the observation of early lethality in mice homozygous for null alleles of Wnt3. To our knowledge, this is the first report of a mutation in a WNT gene associated with a Mendelian disorder. The identification of a WNT3 mutation in tetra-amelia indicates that WNT3 is required at the earliest stages of human limb formation and for craniofacial and urogenital development.

Amelia/ectromelia in association with scoliosis in three commercial layer hens (Gallus gallus forma domestica)

Three wingless "healthy" pullet hens were serendipitously discovered at a grow-out facility for an egg-production ranch. Two of the birds were amelic and one was ectromelic. The defect in these chickens differs from the previously reported wingless mutations in that all three affected birds also had scoliosis. The birds also differed from previously reported scolitic mutant chickens in that they were wingless. Although the combination of amelia and scoliosis has been reported in humans, this is the first report of the combination in an animal species.

Molecular basis of autosomal recessive diseases among the Palestinian Arabs

In the review of the literature, 71 different autosomal recessive diseases have been delineated that are relatively frequent among Palestinian Arabs. Among those, in 40 the mutation(s) responsible for the diseases are known. Fourteen of these disorders were caused by a single mutation, while the other 26 were due to multiple mutations. Most of the mutations were found in homozygosity among the affected patients. It is probable that the high frequency of most of the genetic diseases among the Palestinian Arabs is due to a founder effect as the result of the high consanguinity rates in this population. However, in some cases the high frequency was demonstrated to be secondary to the presence of multiple mutations, either allelic or in different genes in a small geographic region. This phenomenon remains unexplained but may be secondary to a selective advantage to the carriers, either specific to the region or to the population.

Tetra-amelia and splenogonadal fusion in Roberts syndrome

Roberts-SC phocomelia syndrome comprises limb deficiencies of variable severity, facial clefts, and other anomalies. Tetra-amelia may also be associated with facial clefts and similar anomalies. We report on a female infant with severe tetra-amelia, micrognathia, cleft palate, splenogonadal fusion, and premature centromere separation. We propose that this represents the severe expression of the Roberts-SC phocomelia syndrome.

Zimmer phocomelia: delineation by principal coordinate analysis

We present a 46,XX stillborn fetus with tetraphocomelia, absence of ears, severe hypoplasia of nose, cleft palate, pulmonary hypoplasia, imperforate anus and vagina, and phallus-like structure on an otherwise undefined perineum. The pattern of abnormalities resembles the tetraphocomelic condition described by Zimmer et al. in 1985. Tetraphocomelia, ear/nose hypoplasia with facial clefts, pulmonary hypoplasia, and defects of the caudal end including imperforate anus, and abnormal genitalia constitute a distinct pattern of malformation termed Zimmer phocomelia. Principal coordinate analysis with Gower's similarity index supported the clinical impression that cases reported by Zimmer and the present case are distinct from other phocomelic conditions. Although Zimmer phocomelia is currently referred to as "X-linked amelia," documentation of a female case with a penis-like structure in this report as well as consanguinity in the original family in Zimmer's report indicates that this condition is likely inherited in an autosomal recessive fashion. Zimmer phocomelia may be a more appropriate name than X-linked amelia.

Tri-amelia and phocomelia with multiple malformations resembling Roberts syndrome in a fetus: is it a variant or a new syndrome?

Roberts-SC phocomelia syndrome is a rare autosomal recessive disorder characterized by morphological anomalies such as limb defects and midfacial clefting, and by premature centromeric division in chromosomal study. Although it has been regarded as a single genetic entity and includes various morphologic defects, babies are being reported nowadays with severe facial defects, tetra-amelia, and pulmonary abnormality, yet with normal chromosomal findings. We have added a case resembling Roberts syndrome with various congenital anomalies. A gestation with a fetus was terminated at 24 weeks of gestational age because of multiple fetal anomalies. Postmortem examination revealed a severe mid-facial cleft, tri-amelia and phocomelia, multiple encephaloceles, protruding and hypoteloric eyes, low-set ears, atrial septal defect of ostium secundum type, patent ductus arteriosus, bilateral two-lobed lungs with incomplete lobation, multiple visceral anomalies, a penis without scrotum, abnormal dermoglyphics, and absence of nipples.

Familial recurrence of tracheoesophageal fistula and associated malformations

Tracheoesophageal fistula (TEF) may occur as an isolated malformation or together with other malformations. To determine the recurrence risk of TEF or associated malformations in children and sibs, and to determine the frequency of associated malformations in index patients, we reviewed the Mayo Clinic records of 204 patients with TEF. Also, questionnaires were sent to patients or relatives. Questions were designed to determine whether the patient and relatives had TEF and/or related organ system (including VACTERL) malformations. The VACTERL association is a disorder characterized by 3 or more of the following: vertebral, anal, cardiac, renal, or radial anomalies, and TEF. One hundred twenty-eight families returned a completed questionnaire, and 140 index patients were ascertained based on complete medical records, questionnaire, and/or autopsy. Forty-one (29.3%) of 140 index patients had TEF with one other VACTERL malformation, and twenty-four (17.1%) of 140 index patients had TEF with at least two other VACTERL malformations. Of the 347 sibs of index patients, 5 (1.4%) had one VACTERL malformation each, including 1 sib with esophageal atresia (EA) without TEF. Of the 41 children of index patients, 1 (2.4%) had TEF plus two other VACTERL malformations; another had one non-TEF VACTERL malformation. From our study, the largest reported population of TEF patients to date, we conclude that: 1) nearly half (46%) of patients with tracheoesophageal fistula will exhibit other VACTERL malformations; 2) the recurrence risk for individuals with TEF to have affected children is 2-3%; and 3) there is an increased risk to relatives of TEF patients to exhibit other VACTERL malformations.

New autosomal recessive form of amelia

Amelia is a rare, usually sporadic malformation. We report on a family in which three fetuses had amelia of the upper limbs and variable deficiency of the lower limbs. The fetuses also had minor facial anomalies. Recurrence of the condition in sibs of both sexes suggests autosomal recessive inheritance. Recurrent amelia has been documented in only a few families most often associated with a different set of malformations. Possibly, mutations in more than one gene with different modes of transmission can lead to this severe limb deficiency. We speculate that the mutation found in our cases interferes with formation of the apical ectodermal ridge in the upper limbs and results in its premature degeneration in the lower limbs.

Tetra-amelia, lung hypo-/aplasia, cleft lip-palate, and heart defect: a new syndrome?

We report on a family with two sons affected with tetra-amelia, cleft lip-palate, bilateral agenesis of lungs, and heart defects. These two cases support the previous suggestions that this complex entity may indeed represent a new syndrome. However, the mode of inheritance is still not clarified.

Congenital abnormalities associated with limb deficiency defects: a population study based on cases from the Hungarian Congenital Malformation Registry (1975-1984)

Limb deficiency defects (LD) occurring among 1,575,904 births in Hungary during 1975-1984 were reviewed. The overall birth prevalence of LD was 1 in 1,816. This paper discusses the nature and distribution of the limb and other defects in the 275 (32%) children who had structural malformations in other systems. Two main forms of classification were used: morphologic and causal. Additional malformations were most commonly seen in infants with amelia, rudimentary limb (RL), radial/tibial (RT), intercalary or central axis (CA) LD and rarely in those with terminal transverse (TT) or ulnar/fibular (UF) defects. Upper limbs (81%) were involved significantly more often than lower limbs (42%) and there were more right-sided defects (83% vs. 71%) due to an excess of right arm involvement especially with radial ray and split hand anomalies. Single limb involvement was relatively common with amelia (88%), UF (82%), RT (50%), and TT (50%) defects. With other LD, multimelic involvement was more characteristic. This was usually symmetric with intercalary and RL defects but asymmetric with CA anomalies and digital deficiencies (DD). From a causal perspective, 17% of cases had genetic disorders, 52% had recognized associations, anomalies, sequences, environmental causes or patterns of unknown origin, and 31% had unknown patterns of malformations. The commonest entities were amnion disruption sequence (16% of cases) and VACTERL association (8%). Both of these disorders showed unusual temporal distribution. As anticipated, patterns of malformations differed with the type of LD. Amelia and digital amputations were often seen with body wall defects, atypical anencephaly or encephalocele, and cleft lip reflecting amnion disruption. Rudimentary limb was seen with anencephaly, omphalocele, renal agenesis, aberrant genitalia, and imperforate anus, reflecting defects of blastogenesis including the cloacal exstrophy and caudal regression sequences and Schisis association. Radial/tibial defects were associated with different patterns depending on whether the limb defects were unilateral or bilateral. Unilateral defects occurred with anomalies suggesting VACTERL association or the facio-auriculo-vertebral anomaly, while bilateral defects occurred more often in genetic or potentially genetic disorders including VACTERL with hydrocephalus. Central axis defects showed three main patterns of association: one reflecting the ectrodactyly-ectodermal dysplasia-clefting syndrome; one with tongue anomalies representing a variant of oro-mandibular-limb (Hanhart) anomaly, and the last with hydronephrosis indicating a group of "acro-renal" syndromes. Strong associations with other anomalies were not seen in the groups with TT, UF, or intercalary defects.

Phocomelia, oligodactyly, and acrania: the Schinzel-Phocomelia syndrome

We report on a girl born with phocomelia of both lower limbs, with 3-toed feet and partial sacral agenesis. She had normal growth of the upper limbs and trunk, and normal intelligence. Ultrasound study performed during the subsequent pregnancy documented a large skull defect with an intact brain. Fetal autopsy following the termination of that pregnancy was not done. We think this is a further report of the phocomelia syndrome with additional anomalies as reported by Schinzel [Hum Genet 84:539-541, 1990].