Holoprosencephaly (HPE) is a common developmental defect of the forebrain and frequently the midface in humans, with both genetic and environmental causes. HPE has a prevalence of 1:250 during embryogenesis and 1:16,000 newborn infants, and involves incomplete development and septation of midline structures in the central nervous system (CNS) with a broad spectrum of clinical severity. Alobar HPE, the most severe form which is usually incompatible with postnatal life, involves complete failure of division of the forebrain into right and left hemispheres and is characteristically associated with facial anomalies including cyclopia, a primitive nasal structure (proboscis) and/or midfacial clefting. At the mild end of the spectrum, findings may include microcephaly, mild hypotelorism, single maxillary central incisor and other defects (Fig. 1). This phenotypic variability also occurs between affected members of the same family. The molecular basis underlying HPE is not known, although teratogens, non-random chromosomal anomalies and familial forms with autosomal dominant and recessive inheritance have been described. HPE3 on chromosome 7q36 is one of at least four different loci implicated in HPE. Here, we report the identification of human Sonic Hedgehog (SHH) as HPE3-the first known gene to cause HPE. Analyzing 30 autosomal dominant HPE (ADHPE) families, we found five families that segregate different heterozygous SHH mutations. Two of these mutations predict premature termination of the SHH protein, whereas the others alter highly conserved residues in the vicinity of the alpha-helix-1 motif or signal cleavage site.

Holoprosencephaly (HPE) is a genetically and phenotypically heterogenous disorder involving the development of forebrain and midface, with an incidence of 1:16,000 live born and 1:250 induced abortions. This disorder is associated with several distinct facies and phenotypic variability: in the most extreme cases, anophthalmia or cyclopia is evident along with a congenital absence of the mature nose. The less severe form features facial dysmorphia characterized by ocular hypertelorism, defects of the upper lip and/or nose, and absence of the olfactory nerves or corpus callosum. Several intermediate phenotypes involving both the brain and face have been described. One of the gene loci, HPE3, maps to the terminal band of chromosome 7. We have performed extensive physical mapping studies and established a critical interval for HPE3, and subsequently identified the sonic hedgehog (SHH) gene as the prime candidate for the disorder. SHH lies within 15-250 kilobases (kb) of chromosomal rearrangements associated with HPE, suggesting that a 'position effect' has an important role in the aetiology of HPE. As detailed in the accompanying report, this role for SHH is confirmed by the detection of point mutations in hereditary HPE patients.

Lung cancer is the first cause of cancer mortality worldwide, and its early detection is currently the main available strategy to improve disease prognosis. While early diagnosis can be successfully achieved through tomography-based population screenings in high-risk individuals, simple methodologies are needed for effective cancer prevention programs. We developed a test, based on the detection of 34 microRNAs (miRNAs) from serum, that could identify patients with early stage non-small cell lung carcinomas (NSCLCs) in a population of asymptomatic high-risk individuals with 80% accuracy. The signature could assign disease probability accurately either in asymptomatic or symptomatic patients, is able to distinguish between benign and malignant lesions, and to capture the onset of the malignant disease in individual patients over time. Thus, our test displays a number of features of clinical relevance that project its utility in programs for the early detection of NSCLC.

Partial absence of the sacrum is a rare congenital defect which also occurs as an autosomal dominant trait; association with anterior meningocoele, presacral teratoma and anorectal abnormalities constitutes the Currarino triad (MIM 176450). Malformation at the caudal end of the developing notochord at approximately Carnegie stage 7 (16 post-ovulatory days), which results in aberrant secondary neurulation, can explain the observed pattern of anomalies. We previously reported linkage to 7q36 markers in two dominantly inherited sacral agenesis families. We now present data refining the initial subchromosomal localization in several additional hereditary sacral agenesis (HSA) families. We excluded several candidate genes before identifying patient-specific mutations in a homeobox gene, HLXB9, which was previously reported to map to 1q41-q42.1 and to be expressed in lymphoid and pancreatic tissues.

Holoprosencephaly (HPE) is the most common brain anomaly in humans, involving abnormal formation and septation of the developing central nervous system. Among the heterogeneous causes of HPE, mutations in the Sonic Hedgehog (SHH) gene have been shown to result in an autosomal dominant form of the disorder. Here we describe a total of five different mutations in the processing domain encoded by exon 3 of SHH in familial and sporadic HPE. This is the first instance in humans where SHH mutations in the domain responsible for autocatalytic cleavage and cholesterol modification of the N-terminal signaling domain of the protein have been observed.

DNA sequence and annotation of the entire human chromosome 7, encompassing nearly 158 million nucleotides of DNA and 1917 gene structures, are presented. To generate a higher order description, additional structural features such as imprinted genes, fragile sites, and segmental duplications were integrated at the level of the DNA sequence with medical genetic data, including 440 chromosome rearrangement breakpoints associated with disease. This approach enabled the discovery of candidate genes for developmental diseases including autism.

No abstract

No abstract