"Anterior interosseous nerve syndrome (Kiloh Nevin Syndrome) revealing Gantzer muscle and simultaneous myasthenia gravis".

There hasn't been a previous case report of the anterior interosseous nerve injury secondary to the presence of the muscle of Gantzer in a patient with myasthenia gravis in literature before. The anterior interosseous nerve compressive syndrome, also known as Kiloh-Nevin syndrome, is a rare disorder comprising less than 1% of all upper limb neuropathies. Establishing the etiology of anterior interosseous nerve compressive syndrome is challenging because of the lack of specific clinical findings or testing. Herein is the case of a 46 years-old male presented with left eye ptosis, ophthalmoparesis, diplopia, and right-hand weakness. On physical examination, the Pinch Grip test was positive. Electromyography studies showed neurogenic atrophy in the muscles innervated by the anterior interosseous nerve, as well as a pathological decrement of the muscle action potential of more than 10% on repetitive nerve stimulation. Concluding that the presence of the Gantzer muscle caused anterior interosseous nerve compressive syndrome was mainly a diagnosis of exclusion, after careful consideration of other possible etiologies including carpal tunnel syndrome, cervical radiculopathy, and Parsonage-Turner Syndrome. Even though anterior interosseous nerve compressive syndrome is very rare, clinical suspicion ought to arise in the presence of weak radial flexor digitorum profundus and flexor pollicis longus muscles. This case highlights the importance of a thorough medical history, a meticulous physical examination, and particularly the significance of electromyography studies in diagnosing different neuropathological entities. When appropriate, these steps offer information crucial to the differential diagnosis and eventual surgical management, assisting physicians in making informed and accurate treatment decisions.

Down syndrome and mouse models.

The past year has seen major advancements in the characterisation of the Ts65Dn mouse model (which is now known to display many features of Down syndrome). A newer model that is trisomic for the region 21 q22.2--previously called 'Down syndrome' region--has been generated and these mice display behavioural and learning defects. Mutations in the genes Minibrain and SOD1 have been implicated in the development of learning defects in Down syndrome and many new genes from human chromosome 21 are being cloned, which should result in the genesis of other models that phenocopy one or more pathologies of the syndrome.

Regulation of Pdha-2 expression is mediated by proximal promoter sequences and CpG methylation.

Spermatogenesis is a complex process requiring the coordinate expression of a number of testis-specific genes. One of these, Pdha-2, codes for the murine spermatogenesis-specific isoform of the E1a subunit of the pyruvate dehydrogenase complex. To begin to delineate the mechanisms regulating its expression in vivo, we have generated transgenic mice lines carrying Pdha-2 promoter deletion constructs. Here we report that transgenic mice harboring a construct containing only 187 bp of promoter and upstream sequences (core promoter) is sufficient for directing the testis-specific expression of a chloramphenicol acetyltransferase (CAT) reporter gene. Like the endogenous Pdha-2, the CAT gene is expressed in testis in a stage-specific manner. Our studies also show a correlation between CpG methylation within the core promoter and its capacity to regulate transcription. In NIH 3T3 cell lines stably transfected with the Pdha-2 core promoter-CAT construct, high levels of CAT reporter expression are observed, whereas the endogenous Pdha-2 gene is repressed. In these cells, the CpG dinucleotides residing within the transfected promoter are hypomethylated whereas those residing in the endogenous promoter are methylated. Furthermore, promoter activity can be abated by the in vitro methylation of its CpG dinucleotides. DNase I footprint analysis indicates that at least one site for the methylation-mediated repression may occur through the ATF/cyclic AMP response element binding element located within the core promoter. Mutations within this element reduces activity to approximately 50% of the wild-type promoter activity. These results suggest that tissue-specific gene expression may be modulated by other mechanisms in addition to specific transcription factor availability and cooperativity. We propose that methylation may be a mechanism by which repression of the testis-specific Pdha-2 gene is established in somatic tissue.

The nfkb1 promoter is controlled by proteins of the Ets family.

The gene encoding NFKB1 is autoregulated, responding to NF-kappa B/Rel activation through NF-kappa B binding sites in its promoter, which also contains putative sites for Ets proteins. One of the Ets sites, which we refer to as EBS4, is located next to an NF-kappa B/Rel binding site, kB3, which is absolutely required for activity of the promoter in Jurkat T cells in response to activation by phorbol 12-myristate 13-acetate (PMA), PMA/ionomycin, or the Tax protein from human T cell leukemia virus type I. We show that EBS4 is, required for the full response of the nfkb1 promoter to PMA or PMA/ionomycin in Jurkat cells. EBS4 is bound by Ets-1, Elf-1, and other species. Overexpression of Ets-1 augments the response to PMA/ionomycin and this is reduced by mutation of EBS4. Elf-1 has less effect in conjunction with PMA/ionomycin, but by itself activates the promoter 12-fold. This activation is only partly affected by mutation of EBS4, and a mutant promoter that binds Ets-1, but not Elf-1, at the EBS4 site responds to PMA/ionomycin as efficiently as the wild-type. Ets proteins may be responsible for fine-tuning the activity of the nfkb1 gene in a cell-type-specific manner.

The Ets1 proto-oncogene is upregulated by retinoic acid: characterization of a functional retinoic acid response element in the Ets1 promoter.

The v-ets oncoprotein and its progenitor Ets1 belong to a family of transcription factors that are related by an 85 amino acid conserved DNA binding domain, the ets domain. Ets1 plays important role(s) in control of cell proliferation, differentiation and apoptosis. Abnormal expression of Ets1 could lead to disruption of these processes and contribute to development of malignancy. Retinoic acid (RA) inhibits proliferation, induces differentiation and regulates apoptosis in many different cell types. Here, we demonstrate that RA treatment increases the expression of Ets1 mRNA, but not that of Ets2, Elk1 or Fli1 in MC3T3-E1 cells. Ets1 induction is detectable after 4 h, can be maintained for at least 14 days, and is inhibited by Actinomycin D, which suggests that RA regulation of Ets1 occurs at the transcriptional level. The promoter region of Ets1 contains four retinoic acid response element (RARE) half sites located at -94, -152, -1765 and -2252 from the translation start site. We show that RARbeta is expressed by MC3T3-E1 cells in the presence of RA and demonstrate that it binds to the -94 RARE half site. Furthermore, RA induces transcription of Ets1 promoter-reporter constructs containing this RARE half site.

ETS1, NFkappaB and AP1 synergistically transactivate the human GM-CSF promoter.

Activation of helper T cells results in coordinate expression of a number of cytokines involved in differentiation, proliferation and activation of the haematopoietic system. Granulocyte-macrophage colony stimulating factor (GM-CSF) is one such cytokine, whose increased expression results mostly from increases in transcription. Cis-acting elements with NFkappaB, AP1 and ETS-like binding motifs have been identified in the promoter region of the GM-CSF gene, and are important or essential for transcriptional activity following T cell activation. ETS1 is a transcription factor of the ETS family that is expressed in T cells. We have previously shown that ETS1 can transactivate GM-CSF in Jurkat T cells, but only after the cells have been stimulated by treatment with PMA and ionomycin, agents that mimic T cell activation. Thus we proposed that ETS1, which is expressed constitutively in Jurkat cells, may act in concert with PMA/ionomycin inducible factors. Here we show that ETS1 can transactivate a GM-CSF reporter construct in unstimulated Jurkat cells, providing that either NFkappaB or AP1 transcription factors are supplied by co-transfection. We confirm that binding of endogenous NFkappaB and AP1 is induced following PMA/ionomycin treatment of T cells. Transactivation by ETS1, NFkappaB and AP1 is synergistic, and mutation of the individual binding sites reveals that the transcriptional activities of these factors are interdependent. Our results suggest that constitutive ETS1, and inducible NFkappaB and AP1, cooperate as part of a higher order transcriptional complex in activated T cells.

ETS1 and ETS2 in p53 regulation: spatial separation of ETS binding sites (EBS) modulate protein: DNA interaction.

p53 is an extensively studied tumor suppressor gene implicated in the genesis of a large number of varied tumors. However, the pathways of regulation for the wild-type p53 gene and its product are as yet unknown. In situ hybridization analyses of ETS1 and ETS2 expression during mouse embryogenesis, have shown a pattern similar to that of p53 gene expression. Significantly, we have identified several ETS-binding sites (EBS) in the promoter regions of the human and mouse p53 genes. In the human promoter two of these EBS are present in the form of a palindrome, with the two EBS cores being separated by four nucleotides. This report shows that the EBS palindrome of the human p53 promoter has a high affinity for ETS1 and ETS2 and that such binding interaction intracellularly is able to activate the transcription of a CAT reporter gene by 5-10-fold using COS cells. To investigate whether the spacing between the two EBS cores influences the DNA binding activity, we synthesized oligonucleotides with increasing distances (4,12,16, and 20 bases respectively) between the two EBS cores of the palindrome. We observed an inverse correlation between an increasing distance in the two EBS cores of the palindrome and the ETS1 and ETS2 DNA binding activity respectively. Interestingly, optimal DNA binding activity was observed when the distance between the two EBS cores was four bases, identical to that which occurs in the natural promoter. Furthermore we show that the p53 mRNA is expressed at higher levels in NIH3T3 cells overexpressing ETS2 gene product, suggesting that the ETS2 transcription factor is a likely candidate for regulating the expression of p53 in vivo.

FLI1 and EWS-FLI1 function as ternary complex factors and ELK1 and SAP1a function as ternary and quaternary complex factors on the Egr1 promoter serum response elements.

The ETS gene products are a family of transcriptional regulatory proteins that contain a highly conserved and structurally unique DNA binding domain, termed the ETS domain. Several ETS proteins bind to DNA as monomers, however it has been shown that the DNA binding activity is enhanced or modulated in the presence of other factors. By differential display and whole genome PCR techniques, we have recently shown that the Erg1 gene is a target for ETS proteins. The Egr1 promoter contains multiple ETS binding sites, three of which exist as parts of two serum response elements (SREI and SREII). The SRE is a cis-element that regulates the expression of many growth factor responsive genes. ELK1 and SAP1a have been shown to form ternary complexes with SRF on the SRE located in the c-fos promoter. Similarly, we examined whether the ELK1, SAP1a, FLI1, EWS-FLI1, ETS1, ETS2, PEA3 and PU.1 proteins can form ternary complexes with SRF on the Egr1 SREI and II. Our results demonstrate that indeed ELK1, SAPla, FLI1 and EWS-FLI1 are able to form ternary complexes with SRF on Egr1 SREs. In addition, ELK1 and SAP1a can also form quarternary complexes on the Egr1 SREI. However, the proteins ETS1, ETS2, PEA3 and PU.1 were unable to form ternary complexes with SRF on either the Egr1 or c-fos SREs. Our data demonstrate that FLI1 and EWS-FLI1 constitute new members of a subgroup of ETS proteins that can function as ternary complex factors and further implicate a novel function for these ETS transcription factors in the regulation of the Egr1 gene. By amino acid sequence comparison we found that, in fact, 50% of the amino acids present in the B-box of SAP1a and ELK1, which are required for interaction with SRF, are identical to those present in both FLI1 (amino acids 231- 248) and EWS-FLI1 proteins. This B-box is not present in ETS1, ETS2, PEA3 or PU.1 and these proteins were unable to form ternary complexes with SRF and Egrl-SREs or c-fos SRE. Furthermore, deletion of 194 amino terminal amino acids of FLI1 did not interfere with its ability to interact with SRF, in fact, this truncation increased the stability of the ternary complex. The FLI1 protein has a unique R-domain located next to the DNA binding region. This R-domain may modulate the interaction with SRF, providing a mechanism that would be unique to FLI1 and EWS-FLI1, thus implicating a novel function for these ETS transcription factors in the regulation of the Egr1 gene.

ETS1 transactivates the human GM-CSF promoter in Jurkat T cells stimulated with PMA and ionomycin.

Activation of T helper cells results in coordinate expression of a number of cytokines involved in differentiation, proliferation and activation of the haematopoietic system. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is one such cytokine whose increased expression results partly from increases in transcription. Cis-acting elements with NF kappa B, AP-1 and ETS-like motifs have been identified in the promoter region of the GM-CSF gene, which are important for transcriptional activity following PMA and ionomycin stimulation. A number of the ETS family of transcription factors are expressed in T cells, including ETS1 and ELF1. Here we describe the ability of these factors to interact with a site (GM5), located within the CLE0 element, -47 to -40 upstream of the GM-CSF transcription initiation site. Exogenous ETS1, but not ELF1, can transactivate GM-CSF, through the GM5 site, in a PMA/ionomycin dependent manner. Other unidentified ETS-like factors present in Jurkat cells are also capable of binding GM5. Mutation of the core ETS binding site from -GGAA- to -GGAT- prevents the binding of ETS-like factors with the exception of ETS1. The GM-CSF promoter, modified in this way to be ETS1 specific, is fully responsive to PMA/ionomycin induction, in addition to ETS1 transactivation in the presence of PMA and ionomycin. Together these data suggest that ETS1 may be involved in mediating the increased GM-CSF production associated with T cell activation.

Human ERG is a proto-oncogene with mitogenic and transforming activity.

The ETS related gene, ERG, is one of 20 or more genes belonging to the ETS family of transcription factors. Translocation of the ERG gene t(21;22) results in the chimeric fusion transcript seen in approximately 10% of Ewings sarcomas. In addition, recent studies have shown that a reciprocal translocation t(21;16) of ERG gives rise to two aberrant transcripts seen in some forms of acute myeloid leukaemia. In vitro studies have linked the up regulation of ERG expression with stromal cell independence in erythroleukemic clones and shown that the ERG related genes ETS1 and ETS2 have a mitogenic and transforming activity when overexpressed in NIH3T3 cells. Interestingly ERGB/FLI-1, which is also involved in Ewings sarcoma translocations and shares a very high sequence identify with ERG has been reported to be unable to transform NIH3T3 cells. In this study we investigate the effects of overexpression of ERG on cell proliferation, factor dependence, growth in soft agar and tumorigenesis in nude mice. An ERG expression construct with the human ERG2 cDNA driven by the sheep metallothionein la promoter (sMTERG) was transfected into NIH3T3 cells. Clonal cell lines overexpressing ERG were established. The cell lines became morphologically altered, grew in low serum and serum free media and gave rise to colonies in soft agar suspension. Furthermore, we demonstrate that after subcutaneous injection these clones grow as solid tumors in nude mice. These data demonstrate that c-ERG is a proto-oncogene capable of transforming NIH3T3 cells. Therefore, overexpression or inappropriate expression of ERG may contribute to oncogenesis.

A novel transcription factor, ELF5, belongs to the ELF subfamily of ETS genes and maps to human chromosome 11p13-15, a region subject to LOH and rearrangement in human carcinoma cell lines.

The ETS transcription factors are a large family implicated in the control of cellular proliferation and tumorigenesis. In addition, chromosomal translocations involving ETS family members are associated with a range of different human cancers. Given the extensive involvement of ETS factors in tumorigenesis, it becomes important to identify any additional ETS genes that may also play oncogenic roles. We identify a novel gene, ELF5, that appears to belong to the ELF (E74-like-factor) subfamily of the ETS transcription factor family, based upon similarity within the 'ETS domain'. ELF5 displays a similar, but more restricted, expression pattern to that of the newly isolated epithelium-specific ETS gene, ELF3. Unlike most other ETS family members, ELF5 is not expressed in hematopoietic compartments, but is restricted to organs such as lung, stomach, kidney, prostate, bladder and mammary gland. ELF5 is localized to human chromosome 11p13-15, a region that frequently undergoes loss of heterozygosity (LOH) in several types of carcinoma, including those of breast, kidney and prostate. We find that ELF5 expression is not detectable in a number of carcinoma cell lines, some of which display loss or rearrangement of an ELF5 allele. Similar to other ETS family members, ELF5 displays specific binding to DNA sequences containing a GGAA-core. In addition, ELF5 is able to transactivate through these ETS sequences, present upstream from a minimal promoter. Our data suggest that ELF5 may play roles in mammary, lung, prostate and/or kidney function, and possibly also in tumorigenesis.

A novel epithelial-expressed ETS gene, ELF3: human and murine cDNA sequences, murine genomic organization, human mapping to 1q32.2 and expression in tissues and cancer.

The ETS family of genes are implicated in cancers such as Ewings sarcoma, acute myeloid leukemia and chronic myelomonocytic leukemia. Further, they have important functions in embryonic development. Hence, identification and characterization of members of this family are important. We identify a novel ETS family member, ELF3, and report its human and murine cDNA sequences. The mouse cDNA has an alternatively spliced transcript with an extra 60 bp inserted. Hence we present the organization of the murine Elf3 gene together with its exon/intron structure. This gene consists of 9 exons and 8 introns spanning 4.8 kb. ELF3 binds and transactivates ETS sequences and interestingly also shows the ability to bind a GGAT-like purine core, a preferential ETS1/ETS2 type binding site. The expression of ELF3, unlike most other ETS family members, is absent in hematopoietic cells and hematopoietic organs in humans and mice. Intriguingly, the gene is specifically expressed in cell lines of epithelial origin and in organs such as lung, stomach, intestine, kidney that have specialized epithelial cells. We localize the human gene to 1q32.2, a region that is amplified in epithelial tumors of the breast, lung and prostate. Finally, we show that ELF3 expression is increased in a lung carcinoma and adenocarcinoma, as compared to normal tissue. ELF3 is also expressed in cell lines derived from lung cancers. These results suggest that this novel ETS gene may be involved in lung tumorigenesis.

The chromosome 21 transcription factor ETS2 transactivates the beta-APP promoter: implications for Down syndrome.

The gene that codes for beta-amyloid precursor protein (beta-APP), a protein centrally involved in senile plaque formation in Down syndrome (DS) and Alzheimer's disease (AD), is located on chromosome 21. In DS beta-APP expression is three- to fourfold higher than what is expected from the 1.5-fold increased gene load, suggesting that other genes on chromosome 21 directly or indirectly can further up-regulate beta-APP. Here we show that the chromosome 21 transcription factor ETS2 transactivates the beta-APP gene via specific Ets binding sites in the beta-APP promoter and, in this respect, cooperates with the transcription factor complex AP1. We further show that brains and primary neuronal cultures from Ets2 transgenic mice, as well as 3T3 fibroblasts that overexpress ETS2, display molecular abnormalities also seen in DS, such as elevated expression of beta-APP protein, an increase in presenilin-1 and increased beta-amyloid production. We conclude that ETS2 is a transcriptional regulator of beta-APP and that overexpression of ETS2 in DS may play a role in the pathogenesis of the brain abnormalities in DS and possibly AD.

Regulation of the human stress response gene GADD153 expression: role of ETS1 and FLI-1 gene products.

We have previously shown that ETS transcription factors, regulate cell growth and differentiation, and ETS1 and ETS2 are able to transcriptionally regulate wt p53 gene expression. In the present study we show that the ETS transcription factors also play a role in regulating expression of GADD153, a wt p53 inducible gene, which induces growth arrest and apoptosis in response to stress signals or DNA damage. We report the presence of a single EBS in the human GADD153 promoter, and that the GADD45 gene promoter lacks EBSs. The GADD153 promoter EBS shows a very high affinity for ETS1 and FLI-1 gene products. In addition, our data show that both ETS1 and FLI-1 strongly activate transcription of the GADD153 EBS linked to the CAT reporter gene. Our results also demonstrate how ETS1 and FLI-1 specifically regulate GADD153 expression. In addition, ectopic ETS2 protein expression resulted in only a weak induction of the same CAT reporter construct. The ETS1 and FLI-1 proteins provide a novel mechanism of activation for GADD153, allowing these two ETS genes to control its expression during cell growth and differentiation, rather than in response to oxidative stress.

Desrt, an AT-rich interaction domain family transcription factor gene, is an early marker for nephrogenic mesoderm and is expressed dynamically during mouse limb development.

Desrt is a mouse gene of the AT-rich interaction domain family of transcription factors. Here we describe the temporal and spatial pattern of expression of Desrt during mouse organogenesis. Desrt expression is first detected in the intermediate plate mesoderm, providing an early embryonic marker for this tissue, and subsequently in the nephrogenic cords of the urogenital ridges. A highly dynamic expression pattern is observed in the developing limb, implicating Desrt in limb patterning. Desrt is also detected in the myotome of the somites, the oro-naso-pharyngeal ectoderm and underlying mesenchyme, otic vesicles, the gut and its derivatives, and transiently in the liver.

Cathepsin K knockout mice develop osteopetrosis due to a deficit in matrix degradation but not demineralization.

Cathepsin K is a cysteine protease expressed predominantly in osteoclasts. Activated cathepsin K cleaves key bone matrix proteins and is believed to play an important role in degrading the organic phase of bone during bone resorption. Mutations in the human cathepsin K gene have been demonstrated to be associated with a rare skeletal dysplasia, pycnodysostosis. The degree of functional activity of the mutated forms of cathepsin K in these individuals has not been elucidated, but is predicted to be low or absent. To study the role of cathepsin K in bone resorption, we have generated mice deficient in the cathepsin K gene. Histologic and radiographic analysis of the mice revealed osteopetrosis of the long bones and vertebrae, and abnormal joint morphology. X-ray microcomputerized tomography images allowed quantitation of the increase in bone volume, trabecular thickness, and trabecular number in both the primary spongiosa and the metaphysis of the proximal tibiae. Not all bones were similarly affected. Chondrocyte differentiation was normal. The mice also had abnormalities in hematopoietic compartments, particularly decreased bone marrow cellularity and splenomegaly. The heterozygous animals appeared normal. Close histologic examination of bone histology revealed fully differentiated osteoclasts apposed to small regions of demineralized bone. This strongly suggests that cathepsin K-deficient osteoclasts are capable of demineralizing the extracellular matrix but are unable to adequately remove the demineralized bone. This is entirely consistent with the proposed function of cathepsin K as a matrix-degrading proteinase in bone resorption.

Analysis of heat shock protein 70 in human chromosome 21 containing hybrids.

An Hsp70 gene, HspA3, has been given provisional assignment to chromosome 21 based on the heat induced expression of a 70 kDa protein in a Chinese hamster ovary-human hybrid cell line. This assignment has not been supported by hybridization data or by cloning of the gene. The aim of the current study is to clarify this localization. We have analysed a series of Chinese hamster ovary-human hybrid lines containing human chromosome 21 by two-dimensional gel electrophoresis and Western blot analysis with anti-Hsp70 antibodies. Only one of these, hybrid 72532-X6, was found to contain an additional Hsp70 protein. Three other hybrid cell lines spanning different parts of chromosome 21 did not contain any additional Hsp70 proteins. The Hsp70 protein in 72532-X6 is constitutively expressed and is not heat inducible. Southern blot analysis indicates that this protein is not the major human cognate protein, Hsp73 (Hsp70-8), but may be one of the other cognate Hsp70s. Our data indicate that hybrid cell lines containing human chromosome 21 do not express a human Hsp70, as has been reported previously. The recent report that the hybrid cell line used to make this claim also contains other human chromosome fragments leads us to conclude that an Hsp70 gene is not localized on human chromosome.

Binding of interferon-alpha and -beta to a component of the human type I interferon receptor expressed in simian cells.

The type I interferons (IFNs) are a family of homologous cytokines that compete for receptor binding. Past experiments with a cloned human IFN-alpha receptor component (designated herein as HuIFNAR-1) transfected into different cell backgrounds have given contradictory results in terms of binding and signalling after exposure of cells to different human type I IFNs. In order to investigate the binding specificity of human type I IFN subtypes to HuIFNAR-1, a cDNA encoding HuIFNAR-1 was transfected into simian COS cells. HuIFNAR-1 expression in COS cells, which was confirmed by Northern blot analysis, resulted in increased binding of 125I-labelled HuIFN-alpha 2 and -beta. These data support the participation of this receptor component in ligand binding, probably in association with other receptor components.

Detailed mapping of the ERG-ETS2 interval of human chromosome 21 and comparison with the region of conserved synteny on mouse chromosome 16.

We have carried out a detailed annotation of 550 kb of genomic DNA on human chromosome 21 containing the ERG and ETS2 genes. Comparative genomic analysis between this region and the interval of conserved synteny on mouse chromosome 16 indicated that the order and orientation of the ERG and ETS2 genes were conserved and revealed several regions containing potential conserved noncoding sequences. Four pseudogenes including those for small protein G, laminin receptor, human transposase protein and meningioma-expressed antigen were identified. A potentially novel gene (C21orf24) with alternative mRNA transcripts, consensus splice donor and acceptor sites, but no coding potential nor murine orthologue, was identified and found to be expressed in a range of human cell lines. We have identified four novel splice variants that arise from a previously undescribed 5' exon of the human ERG gene. Comparison of the cDNA sequences enabled us to determine the complete exon-intron structure of the ERG gene. We have also identified the presence of noncoding RNAs in the first and second introns of the ETS2 gene. Our studies have important implications for Down syndrome as this region contains multiple mRNA transcripts, both coding and potentially noncoding, that may play as yet undescribed roles in the pathogenesis of this disorder.