Holt-Oram syndrome is caused by mutations in TBX5, a member of the Brachyury (T) gene family.

Holt-Oram syndrome is a developmental disorder affecting the heart and upper limb, the gene for which was mapped to chromosome 12 two years ago. We have now identified a gene for this disorder (HOS1). The gene (TBX5) is a member of the Brachyury (T) family corresponding to the mouse Tbx5 gene. We have identified six mutations, three in HOS families and three in sporadic HOS cases. Each of the mutations introduces a premature stop codon in the TBX5 gene product. Tissue in situ hybridization studies on human embryos from days 26 to 52 of gestation reveal expression of TBX5 in heart and limb, consistent with a role in human embryonic development.

Antenatal detection of cleft lip with or without cleft palate: incidence of associated chromosomal and structural anomalies.

OBJECTIVE: To ascertain how many fetuses with prenatally diagnosed cleft lip with or without cleft palate have associated congenital structural and/or chromosomal abnormalities and whether there is an association with the anatomical type of cleft lip or palate. METHODS: This was a retrospective review of infants referred to the North-West England Regional Cleft Lip and Palate (CLAP) team between January 2000 and January 2006. Referrals made to the Regional Fetal Management Unit (FMU) in the same time period were investigated to identify the corresponding antenatal ultrasound findings and data on termination of pregnancy and intrauterine fetal death. RESULTS: Over the 6-year period investigated, 570 infants were referred to the FMU and/or CLAP team. Among these, there were 24 terminations of pregnancy, two intrauterine fetal deaths and one early neonatal death identified. Data on 69 of the 543 patients that survived were incomplete. Of 188 cases with unilateral and 34 cases with bilateral cleft lip +/- palate there were no karyotypical abnormalities without other structural abnormalities. The incidence of associated structural abnormalities varied with the anatomical type of cleft: that of unilateral cleft lip +/- palate was 9.8% (19/194), that of bilateral cleft lip and palate was 25% (11/44) and that of midline cleft lip and palate was 100% (11/11). None of 252 cases with isolated cleft palate was identified antenatally; of these, 5.6% (n = 14) had either karyotypical or associated structural abnormalities and 21.0% (n = 53) had a genetic syndrome as an underlying diagnosis. CONCLUSIONS: It is essential to tailor the antenatal counseling of patients to the specific scan diagnosis, considering both the anatomical type of cleft and the presence or absence of associated abnormalities. It is inappropriate to offer invasive testing to all patients. The use of three-dimensional ultrasound as an adjunct should be considered in these patients to improve the accuracy of prenatal diagnosis.

SRY, SOX9, and DAX1 expression patterns during human sex determination and gonadal development.

SRY, SOX9, and DAX1 are key genes in human sex determination, by virtue of their associated male-to-female sex reversal phenotypes when mutated (SRY, SOX9) or over-expressed (DAX1). During human sex determination, SRY is expressed in 46,XY gonads coincident with sex cord formation, but also persists as nuclear protein within Sertoli cells at 18 weeks gestation. High-level SOX9 expression in the sex cords of the testis parallels that seen during mouse development, however in humans, SOX9 transcripts also are detected in the developing ovary. Low-level DAX1 expression predates peak SRY expression by at least 10 days, and persists in Sertoli cells throughout the entire sex determination period. In Dosage Sensitive Sex reversal, the anti-testis properties of DAX1 over-expression could act prior to the peak effects of SRY and continue during the period of SOX9 expression. These findings highlight expression differences for the SRY, SOX9, and DAX1 genes during sex determination in humans and mice. These results provide a direct framework for future investigation into the mechanisms underlying normal and abnormal human sex determination.

Isolation, characterisation and embryonic expression of WNT11, a gene which maps to 11q13.5 and has possible roles in the development of skeleton, kidney and lung.

The Wnt gene family encodes a set of signalling molecules, thought to play an important role in key processes of embryonic development. In vertebrates as a whole 20 different Wnt genes have been identified to date, however, a complement of only 16 have been identified in man and for some of these the complete coding sequences are unavailable. We have recently isolated the full-length cDNA sequence of a new human WNT gene, WNT11, investigated its genomic organisation and performed detailed expression studies in early human embryos. These have shown that the expression of human WNT11 is restricted to the perichondrium of the developing skeleton, lung mesenchyme, the tips of the ureteric buds and other areas of the urogenital system and the cortex of the adrenal gland. This, for the first time, provides information for the embryonic expression of human WNT11. We have mapped WNT11 to 11q13.5 and this together with its expression in the perichondrium of the developing skeleton, makes it a plausible candidate gene for HBM, which has been previously linked to markers from this region.

Human post-implantation embryo collection: medical and surgical techniques.

Knowledge of the genetic control of early human development is limited with most information being extrapolated from studies in animal models. There is compelling evidence that undertaking gene expression studies in human embryos can be expected to dramatically enhance our understanding of embryonic formation and malformation. Such studies require the systematic and coordinated collection, storage and study of human embryos. We have successfully collected intact embryos from cases undergoing termination of pregnancy (TOP). Embryonic material was collected from 62% of attempts using a technique of surgical aspiration carried out under ultrasound guidance. Collection rates were lower after medical termination of pregnancy (41%) although the proportion of undisrupted embryos was identical with the two methods (26%). Surgical aspiration provided intact embryos between Carnegie stages (CS) 16-22 while earlier developmental stages were collected from medical terminations. Our collection of over 60 intact specimens, spanning Carnegie stages 10 to 22 (about 21 to 53 days of development) covers a huge window of critical developmental events and hence represents an exciting and valuable research resource.

Placental expression of anti-angiogenic proteins in mirror syndrome: a case report.

Mirror syndrome is a rare disorder in which fetal hydrops is associated with maternal oedema, proteinuria and hypertension. The aetiology of the maternal condition is unknown, but it is thought to be related to preeclampsia. Few descriptions exist of placental morphology in mirror syndrome, but placentomegaly is consistently observed. In this case placental morphology showed villous oedema and syncytial nuclear aggregates where villi were in direct contact. Immunoperoxidase staining for VEGFR1 and Endoglin was more intense in mirror syndrome compared to gestational-age matched controls,and at a similar level to a case of preeclampsia. Placentally-derived anti-angiogenic factors may be involved in the pathogenesis of mirror syndrome.

A new splint for use in axillary surgery.

The surgical options for the treatment of axillary hidradenitis suppurativa are discussed. A new light-weight splint is described which will allow comfortable immobilisation of the shoulder at 45 degrees yet permit full forearm movement and adequate access to the axilla for dressings. We have found the splint of benefit in the management of this conditions by promoting the primary healing of split skin grafts.

Investigation of the epidemiology and prenatal diagnosis of holoprosencephaly in the North of England.

OBJECTIVE: This study was undertaken to provide epidemiologic data on the prevalence of holoprosencephaly and to assess the sensitivity of routine ultrasonographic screening in a low-risk population. STUDY DESIGN: A population-based register of congenital abnormalities was used to identify reported cases of holoprosencephaly between 1985 and 1998. Sources included fetal losses, termination for fetal anomaly, stillbirths, and live births. Prenatal diagnoses and pregnancy outcomes were determined. RESULTS: Sixty-eight cases of holoprosencephaly were found among 531,686 births. The total prevalence (including pregnancy terminations) was 1.2 cases/10,000 registered births, and the birth prevalence (affected live births and stillbirths at >24 weeks' gestation) was 0.49 cases/10,000 births. Prenatal diagnosis was achieved in 71% of cases, rising to 86% during the second half of the study period; the mean gestational age at diagnosis was 19.8 weeks' gestation. Chromosomal abnormalities (75% of which were trisomy 13) were present in 38% of cases in which a karyotype was established. All those with aneuploidy (80% diagnosed prenatally) had other nonfacial anomalies; additional anomalies were also common in the euploid group (61% diagnosed prenatally), with 90% having facial abnormalities and 70% having other abnormalities. CONCLUSION: The prevalence of holoprosencephaly in second-trimester pregnancies was about 1 in 8000. Prenatal detection reached 86% with a routine anomaly scanning program. The etiology could usually be determined, which has important implications for recurrence risks.

A novel mammalian wnt gene, WNT8B, shows brain-restricted expression in early development, with sharply delimited expression boundaries in the developing forebrain.

Our current knowledge of mammalian forebrain development is meagre. The comparatively few relevant anatomical landmarks are, however, being supplemented by gene expression studies which are able to identify subsets of anatomical structures. We previously described cloning, subchromosomal localization and preliminary structural characterization of the human WNT8B gene, the first mammalian Wnt8b gene to be reported. Wnt genes encode intercellular signalling molecules which play a variety of critical roles in early development, including, in several cases, a presumed role in brain development. In the current report we present the full-length cDNA sequence and genomic organization of the human Wnt8b gene and report studies of expression of the Wnt8b gene in human and mouse embryos. The human and mouse expression patterns appeared identical and were restricted to the developing brain, with the great majority of expression being found in the developing forebrain. In the latter case expression was confined to the germinative neuroepithelium of three sharply delimited regions: the dorsomedial wall of the telencephalic ventricles (which includes the developing hippocampus), a discrete region of the dorsal thalamus and the mammillary and retromammillary regions of the posterior hypothalamus. Expression in the developing hippocampus may suggest a role for WNT8B in patterning of this region and subchromosomal localization of the human gene to 10q24 may suggest it as a candidate gene for partial epilepsy in families where the disease has been linked to markers in this region.

Human-mouse differences in the embryonic expression patterns of developmental control genes and disease genes.

Our understanding of early human development has been impeded by the general difficulty in obtaining suitable samples for study. As a result, and because of the extraordinarily high degree of evolutionary conservation of many developmentally important genes and developmental pathways, great reliance has been placed on extrapolation from animal models of development, principally the mouse. However, the strong evolutionary conservation of coding sequence for developmentally important genes does not necessarily mean that their expression patterns are as highly conserved. The very recent availability of human embryonic samples for gene expression studies has now permitted for the first time an assessment of the degree to which we can confidently extrapolate from studies of rodent gene expression patterns. We have found significant human-mouse differences in embryonic expression patterns for a variety of genes. We present detailed data for two illustrative examples. Wnt7a, a very highly conserved gene known to be important in early development, shows significant differences in spatial and temporal expression patterns in the developing brain (midbrain, telencephalon) of man and mice. CAPN3, the locus for LGMD2A limb girdle muscular dystrophy, and its mouse orthologue differ extensively in expression in embryonic heart, lens and smooth muscle. Our study also shows how molecular analyses, while providing explanations for the observed differences, can be important in providing insights into mammalian evolution.