Assignment of ALDH3 to human chromosome 17p11.2 and ALDH5 to human chromosome 9p13

The Concept of Cancer Stem Cells: Elaborating on ALDH1B1 as an Emerging Marker of Cancer Progression

Cancer is a multifactorial, complex disease exhibiting extraordinary phenotypic plasticity and diversity. One of the greatest challenges in cancer treatment is intratumoral heterogeneity, which obstructs the efficient eradication of the tumor. Tumor heterogeneity is often associated with the presence of cancer stem cells (CSCs), a cancer cell sub-population possessing a panel of stem-like properties, such as a self-renewal ability and multipotency potential. CSCs are associated with enhanced chemoresistance due to the enhanced efflux of chemotherapeutic agents and the existence of powerful antioxidant and DNA damage repair mechanisms. The distinctive characteristics of CSCs make them ideal targets for clinical therapeutic approaches, and the identification of efficient and specific CSCs biomarkers is of utmost importance. Aldehyde dehydrogenases (ALDHs) comprise a wide superfamily of metabolic enzymes that, over the last years, have gained increasing attention due to their association with stem-related features in a wide panel of hematopoietic malignancies and solid cancers. Aldehyde dehydrogenase 1B1 (ALDH1B1) is an isoform that has been characterized as a marker of colon cancer progression, while various studies suggest its importance in additional malignancies. Here, we review the basic concepts related to CSCs and discuss the potential role of ALDH1B1 in cancer development and its contribution to the CSC phenotype.

Oxidative and reductive metabolism of lipid-peroxidation derived carbonyls

Extensive research has shown that increased production of reactive oxygen species (ROS) results in tissue injury under a variety of pathological conditions and chronic degenerative diseases. While ROS are highly reactive and can incite significant injury, polyunsaturated lipids in membranes and lipoproteins are their main targets. ROS-triggered lipid-peroxidation reactions generate a range of reactive carbonyl species (RCS), and these RCS spread and amplify ROS-related injury. Several RCS generated in oxidizing lipids, such as 4-hydroxy trans-2-nonenal (HNE), 4-oxo-2-(E)-nonenal (ONE), acrolein, malondialdehyde (MDA) and phospholipid aldehydes have been shown to be produced under conditions of oxidative stress and contribute to tissue injury and dysfunction by depleting glutathione and other reductants leading to the modification of proteins, lipids, and DNA. To prevent tissue injury, these RCS are metabolized by several oxidoreductases, including members of the aldo-keto reductase (AKR) superfamily, aldehyde dehydrogenases (ALDHs), and alcohol dehydrogenases (ADHs). Metabolism via these enzymes results in RCS inactivation and detoxification, although under some conditions, it can also lead to the generation of signaling molecules that trigger adaptive responses. Metabolic transformation and detoxification of RCS by oxidoreductases prevent indiscriminate ROS toxicity, while at the same time, preserving ROS signaling. A better understanding of RCS metabolism by oxidoreductases could lead to the development of novel therapeutic interventions to decrease oxidative injury in several disease states and to enhance resistance to ROS-induced toxicity.

Human aldehyde dehydrogenases: potential pathological, pharmacological, and toxicological impact

Aldehyde dehydrogenases catalyze the pyridine nucleotide-dependent oxidation of aldehydes to acids. Seventeen enzymes are currently viewed as belonging to the human aldehyde dehydrogenase superfamily. Summarized herein, insofar as the information is available, are the structural composition, physical properties, tissue distribution, subcellular location, substrate specificity, and cofactor preference of each member of this superfamily. Also summarized are the chromosomal locations and organization of the genes that encode these enzymes and the biological consequences when enzyme activity is lost or substantially diminished. Broadly, aldehyde dehydrogenases can be categorized as critical for normal development and/or physiological homeostasis (1). even when the organism is in a friendly environment or (2). only when the organism finds itself in a hostile environment. The primary, if not sole, evolved raison d'être of first category aldehyde dehydrogenases appears to be to catalyze the biotransformation of a single endobiotic for which they are relatively specific and of which the resultant metabolite is essential to the organism. Most of the human aldehyde dehydrogenases for which the relevant information is available fall into this category. Second category aldehyde dehydrogenases are relatively substrate nonspecific and their evolved raison d'être seems to be to protect the organism from potentially harmful xenobiotics, specifically aldehydes or xenobiotics that give rise to aldehydes, by catalyzing their detoxification. Thus, the lack of a fully functional first category aldehyde dehydrogenase results in a gross pathological phenotype in the absence of any insult, whereas the lack of a functional second category aldehyde dehydrogenase is ordinarily of no consequence with respect to gross phenotype, but is of consequence in that regard when the organism is subjected to a relevant insult.

RAI1 is a novel polyglutamine encoding gene that is deleted in Smith-Magenis syndrome patients

The human chromosomal band 17p11.2 is a genetically unstable interval. It has been shown to be deleted in patients suffering from Smith-Magenis syndrome. Previous efforts of physical and transcriptional mapping in 17p11.2 and subsequent genomic sequencing of the candidate interval allowed the identification of new genes that might be responsible for the Smith-Magenis syndrome. In this report, one of these genes named RAI1, the human homologue of the mouse Rai1 gene, has been investigated for its contribution to the syndrome. Expression analysis on different human adult and fetal tissues has shown the existence of at least three splice variants. Moreover, the most interesting feature of the gene is the presence of a polymorphic CAG repeat coding for a polyglutamine stretch in the amino terminal domain of the protein.

Spectrum of mutations and sequence variants in the FALDH gene in patients with Sjögren-Larsson syndrome

The gene encoding the human fatty aldehyde dehydrogenase (FALDH) is located on 17p11.2, causing Sjögren-Larsson syndrome (SLS) when mutated. SLS is an autosomal recessive disorder characterized by a combination of mental retardation, congenital ichthyosis, and spastic di- or tetraplegia. We report here on studies of 16 SLS families from Europe and the Middle East, which resulted in identification of 11 different mutations. The spectrum of mutations characterized in the present study are five nucleotide substitutions resulting in amino acid changes, five frameshift mutations introducing a stop codon, and one in-frame deletion with insertion at the same position. We also observed silent sequence variants in the FALDH gene and a base pair substitution in exon 5 that alters aspartic acid to asparagine, all of which are considered polymorphisms.

Transcription mapping in a medulloblastoma breakpoint interval and Smith-Magenis syndrome candidate region: identification of 53 transcriptional units and new candidate genes

The chromosomal band 17p11.2 is associated with a number of neurological disorders and malignant diseases. This region is also characterized by the presence of complex repeat elements that are probably responsible for the frequent occurrence of interstitial deletions, duplications, and isochromosome formation. In the course of the molecular analysis of this interval, an integrated map with YACs, PACs, and cosmids covering approximately 6 Mb was established. Focusing on the 1.4-Mb interval containing the Smith-Magenis syndrome critical region and the breakpoint region for medulloblastomas, we constructed a detailed transcript map between the marker PS2 and the proximal CMT1A repeat. FISH analysis of the PACs allowed determination of the position of the transcripts with respect to the SMS critical region and the presumptive chromosomal breakpoint in medulloblastomas. One PAC (G21100) provided evidence for the presence of a novel complex repeat unit, indicating that there are at least three independent repeat elements within 2 Mb. Five genes were mapped to clone G21100 and are likely to form part of this novel complex sequence repeat. In summary, 53 new transcripts were isolated by using cDNA selection and exon trapping. This included 8 known but previously unmapped genes and 45 novel transcripts. The expression profile of 21 transcripts was determined by RT-PCR. Based on their homologies to known genes or proteins, some of the novel genes are considered candidate genes either for malignant diseases or for the Smith-Magenis syndrome.

Molecular cloning, localization, and developmental expression of mouse brain finger protein (Bfp)/ZNF179: distribution of bfp mRNA partially coincides with the affected areas of Smith-Magenis syndrome

Bfp (brain finger protein) is a member of the RING finger protein family, which is highly expressed in the brain. We have previously shown that one copy of the human bfp gene, mapped at 17p11.2, was actually deleted in six of six Smith-Magenis syndrome (SMS) patients. Now we have isolated the mouse bfp cDNA. Using in situ hybridization and immunohistochemistry, the distribution of mouse bfp mRNA and protein was identified especially in neural cells of the cerebral cortex, hippocampus, lateral amygdaloid nucleus, and ventromedial hypothalamus. In primary culture of the whole brain in a neonatal mouse, the Bfp protein was detected in both neuron and glial cells, and its subcellular localization was predominantly in the nucleus, but some amounts were also found in the cytoplasm. The bfp mRNA was also expressed strongly in the marginal zone of brain vesicles, optic stalk, and cartilage primordium, which are part of the critical tissues frequently involved in SMS patients, and in such tissues as nasal epithelium and primordium of follicles in a 13. 5-dpc embryo. Subsequently, its amount in the developing brain further increased during embryogenesis, reaching the highest level in the adult brain. These findings suggest a possibility that Bfp might be involved in the pathogenesis of Smith-Magenis syndrome as a regulator protein related to neural differentiation and function.

Behavioral phenotype of Smith-Magenis syndrome (del 17p11.2)

Smith-Magenis syndrome (SMS) is a distinct and clinically recognizable multiple congenital anomaly (MCA) and mental retardation syndrome caused by an interstitial deletion of chromosome 17 p11.2. The phenotype of SMS has been well described and includes: a characteristic pattern of physical features; a hoarse, deep voice; speech delay with or without associated hearing loss; signs of peripheral neuropathy; variable levels of mental retardation; and neurobehavioral problems. Although self-injury and sleep disturbance are major problems in SMS, studies are limited on the behavioral phenotype of SMS. This report reviews the current state of knowledge about SMS and presents new data based on syndrome-specific observations by the authors' longitudinal experience working with SMS, specifically related to the behavioral aspects of SMS. This information should have relevance for parents, clinicians, geneticists, and educators involved in the care of individuals with SMS.

Homologous recombination of a flanking repeat gene cluster is a mechanism for a common contiguous gene deletion syndrome

Smith-Magenis syndrome (SMS), caused by del(17)p11.2, represents one of the most frequently observed human microdeletion syndromes. We have identified three copies of a low-copy-number repeat (SMS-REPs) located within and flanking the SMS common deletion region and show that SMS-REP represents a repeated gene cluster. We have isolated a corresponding cDNA clone that identifies a novel junction fragment from 29 unrelated SMS patients and a different-sized junction fragment from a patient with dup(17)p11.2. Our results suggest that homologous recombination of a flanking repeat gene cluster is a mechanism for this common microdeletion syndrome.

Human fatty aldehyde dehydrogenase gene (ALDH10): organization and tissue-dependent expression

Mutations in the fatty aldehyde dehydrogenase gene (ALDH10) are responsible for Sjögren-Larsson syndrome (De Laurenzi et al., 1996). In this study, the expression and the genomic organization of the ALDH10 gene are reported. The gene spans approximately 31 kb and consists of 10 exons and 9 introns. All exon-intron junction sequences match the classical GT/AG rule. Both S1 nuclease protection assay and primer extension study suggest that the transcription initiation site is located 195 nucleotides upstream from the ATG codon. No canonical TATA box can be found in the 5'-flanking sequence of the gene, but a CCAAT-like box was found 58 bp upstream of the putative transcription start site. Sequence analysis of the 5'-flanking region revealed numerous potential binding sites for transcription factors Sp1 and AP-2 and one putative HIP-1 binding site. Northern blot analysis of poly(A)+ RNA from various tissues revealed two mRNA species, with sizes around 4.0 and 2.0 kb, that are derived from the differential use of two polyadenylation sites. Although this gene is expressed in a variety of human tissues, the expression level of ALDH10 in the liver and skeletal muscle appears to be higher than that in other tissues examined.

Multi-disciplinary clinical study of Smith-Magenis syndrome (deletion 17p11.2)

Smith-Magenis syndrome (SMS) is a multiple congenital anomaly, mental retardation (MCA/MR) syndrome associated with deletion of chromosome 17 band p11.2. As part of a multi-disciplinary clinical, cytogenetic, and molecular approach to SMS, detailed clinical studies including radiographic, neurologic, developmental, ophthalmologic, otolaryngologic, and audiologic evaluations were performed on 27 SMS patients. Significant findings include otolaryngologic abnormalities in 94%, eye abnormalities in 85%, sleep abnormalities (especially reduced REM sleep) in 75%, hearing impairment in 68% (approximately 65% conductive and 35% sensorineural), scoliosis in 65%, brain abnormalities (predominantly ventriculomegaly) in 52%, cardiac abnormalities in at least 37%, renal anomalies (especially duplication of the collecting system) in 35%, low thyroxine levels in 29%, low immunoglobulin levels in 23%, and forearm abnormalities in 16%. The measured IQ ranged between 20-78, most patients falling in the moderate range of mental retardation at 40-54, although several patients scored in the mild or borderline range. The frequency of these many abnormalities in SMS suggests that patients should be evaluated thoroughly for associated complications both at the time of diagnosis and at least annually thereafter.

Sjögren-Larsson syndrome is caused by mutations in the fatty aldehyde dehydrogenase gene

Sjögren-Larsson syndrome (SLS) is an inherited neurocutaneous disorder characterized by mental retardation, spasticity and ichthyosis. SLS patients have a profound deficiency in fatty aldehyde dehydrogenase (FALDH) activity. We have now cloned the human FALDH cDNA and show that it maps to the SLS locus on chromosome 17p11.2. Sequence analysis of FALDH amplified from fibroblast mRNA and genomic DNA from 3 unrelated SLS patients reveals distinct mutations, including deletions, an insertion and a point mutation. The cloning of FALDH and the identification of mutations in SLS patients opens up possibilities for developing therapeutic approaches to ameliorate the neurologic and cutaneous symptoms of the disease.