Cloning and genomic organization of the human transforming growth factor-beta type I receptor gene

Molecular Genetic Characterization of Sudden Deaths Due to Thoracic Aortic Dissection or Rupture

BACKGROUND

Sudden deaths due to thoracic aortic dissection or ruptures (TADR) are often investigated by forensic pathologists in the United States. Up to a quarter of reported TADR result from a highly penetrant autosomal dominant single gene variant. Testing genes associated with familial TADR provides an underlying etiology for the cause of death and informs effective sudden death prevention for at-risk family members. At the New York City Office of Chief Medical Examiner (NYC-OCME), TADR cases are routinely tested by the in-house, CAP-accredited Molecular Genetics Laboratory. In this retrospective study, TADR and cardiovascular cases were reviewed to understand the burden of TADR in sudden deaths, value of molecular diagnostic testing in TADR, and genotype-phenotype correlations in a demographically diverse TADR cohort.

METHODS

Between July 2019 and June 2022, cases with in-house cardiovascular genetic testing at NYC-OCME were retrospectively reviewed. Twenty genes associated with familial TADR were analyzed using high throughput massive parallel sequencing on postmortem tissues or bloodspot cards. Variant interpretation was conducted according to ACMG/AMP guidelines.

RESULTS

A total of 1078 cases were tested for cardiovascular genetic conditions, of which 34 (3%) had TADR. Eight of those TADR cases had a pathogenic or likely pathogenic variant (P/LPV), 4 had a variant of uncertain significance (VUS), and 22 cases were negative for variants in TADR genes. The molecular diagnostic yield using the TADR subpanel was 23.5%. The genes with the greatest prevalence of P/LPV were FBN1 (6), followed by TGFBR2 (2), TGFBR1 (1), and MYLK (1). Highly penetrant P/LPV in TGFBR2, FBN1, and TGFBR1 were found in TADR individuals who died younger than 34 years old. Two P/LPV in FBN1 were secondary findings unrelated to cause of death. P/LPV in FBN1 included five truncating variants located in the N-terminal domains and one missense variant involved in the disulfide bonds of the EGF-like domain. All P/LPV in TGFBR1 and TGFBR2 were missense or in-frame deletion variants located in the protein kinase catalytic domain. Three variants were first reported in this study.

CONCLUSIONS

Molecular testing of familial TADR-associated genes is a highly effective tool to identify the genetic cause of TADR sudden deaths and benefits surviving at-risk families.

Species-specific sensitivity to TGFβ signaling and changes to the Mmp13 promoter underlie avian jaw development and evolution

Precise developmental control of jaw length is critical for survival, but underlying molecular mechanisms remain poorly understood. The jaw skeleton arises from neural crest mesenchyme (NCM), and we previously demonstrated that these progenitor cells express more bone-resorbing enzymes including Matrix metalloproteinase 13 (Mmp13) when they generate shorter jaws in quail embryos versus longer jaws in duck. Moreover, if we inhibit bone resorption or Mmp13, we can increase jaw length. In the current study, we uncover mechanisms establishing species-specific levels of Mmp13 and bone resorption. Quail show greater activation of and sensitivity to transforming growth factor beta (TGFβ) signaling than duck; where intracellular mediators like SMADs and targets like Runt-related transcription factor 2 (Runx2), which bind Mmp13, become elevated. Inhibiting TGFβ signaling decreases bone resorption, and overexpressing Mmp13 in NCM shortens the duck lower jaw. To elucidate the basis for this differential regulation, we examine the Mmp13 promoter. We discover a SMAD-binding element and single nucleotide polymorphisms (SNPs) near a RUNX2-binding element that distinguish quail from duck. Altering the SMAD site and switching the SNPs abolish TGFβ sensitivity in the quail Mmp13 promoter but make the duck promoter responsive. Thus, differential regulation of TGFβ signaling and Mmp13 promoter structure underlie avian jaw development and evolution.

The Combinational Use of CRISPR/Cas9 and Targeted Toxin Technology Enables Efficient Isolation of Bi-Allelic Knockout Non-Human Mammalian Clones

Recent advances in genome editing systems such as clustered regularly interspaced short palindromic repeats/CRISPR-associated protein-9 nuclease (CRISPR/Cas9) have facilitated genomic modification in mammalian cells. However, most systems employ transient treatment with selective drugs such as puromycin to obtain the desired genome-edited cells, which often allows some untransfected cells to survive and decreases the efficiency of generating genome-edited cells. Here, we developed a novel targeted toxin-based drug-free selection system for the enrichment of genome-edited cells. Cells were transfected with three expression vectors, each of which carries a guide RNA (gRNA), humanized Cas9 (hCas9) gene, or Clostridium perfringens-derived endo-β-galactosidase C (EndoGalC) gene. Once EndoGalC is expressed in a cell, it digests the cell-surface α-Gal epitope, which is specifically recognized by BS-I-B₄ lectin (IB4). Three days after transfection, these cells were treated with cytotoxin saporin-conjugated IB4 (IB4SAP) for 30 min at 37 °C prior to cultivation in a normal medium. Untransfected cells and those weakly expressing EndoGalC will die due to the internalization of saporin. Cells transiently expressing EndoGalC strongly survive, and some of these surviving clones are expected to be genome-edited bi-allelic knockout (KO) clones due to their strong co-expression of gRNA and hCas9. When porcine α-1,3-galactosyltransferase gene, which can synthesize the α-Gal epitope, was attempted to be knocked out, 16.7% and 36.7% of the surviving clones were bi-allelic and mono-allelic knockout (KO) cells, respectively, which was in contrast to the isolation of clones in the absence of IB4SAP treatment. Namely, 0% and 13.3% of the resulting clones were bi-allelic and mono-allelic KO cells, respectively. A similar tendency was seen when other target genes such as DiGeorge syndrome critical region gene 2 and transforming growth factor-β receptor type 1 gene were targeted to be knocked out. Our results indicate that a combination of the CRISPR/Cas9 system and targeted toxin technology using IB4SAP allows efficient enrichment of genome-edited clones, particularly bi-allelic KO clones.

Novel Ex Vivo Culture Method for the Study of Dupuytren's Disease: Effects of TGFβ Type 1 Receptor Modulation by Antisense Oligonucleotides

Dupuytren's disease (DD) is a benign fibroproliferative disease of the hand. It is characterized by the excessive production of extracellular matrix (ECM) proteins, which form a strong fibrous tissue between the handpalm and fingers, permanently disrupting the fine movement ability. The major contractile element in DD is the myofibroblast (MFB). This cell has both fibroblast and smooth muscle cell-type characteristics and causes pathological collagen deposition. MFBs generate contractile forces that are transmitted to the surrounding collagen matrix. Μajor profibrotic factors are members of the transforming growth factor-β (TGFβ) pathway which directly regulate the expression levels of several fibrous proteins such as collagen type 1, type 3, and α-smooth muscle actin. Molecular modulation of this signaling pathway could serve as a therapeutic approach. We, therefore, have developed an ex vivo “clinical trial” system to study the properties of intact, patient-derived resection specimens. In these culture conditions, Dupuytren's tissue retains its three-dimensional (3D) structure and viability. As a novel antifibrotic therapeutic approach, we targeted TGFβ type 1 receptor (also termed activin receptor-like kinase 5) expression in cultured Dupuytren's specimens by antisense oligonucleotide-mediated exon skipping. Antisense oligonucleotides targeting activin receptor-like kinase 5 showed specific reduction of ECM and potential for clinical application.

Molecular characterization of TGF-β type I receptor gene (Tgfbr1) in Chlamys farreri, and the association of allelic variants with growth traits

BACKGROUND

Scallops are an economically important aquaculture species in Asian countries, and growth-rate improvement is one of the main focuses of scallop breeding. Investigating the genetic regulation of scallop growth could benefit scallop breeding, as such research is currently limited. The transforming growth factor beta (TGF-β) signaling through type I and type II receptors, plays critical roles in regulating cell proliferation and growth, and is thus a plausible candidate growth regulator in scallops.

RESULTS

We cloned and characterized the TGF-β type I receptor (Tgfbr1) gene from Zhikong scallops (Chlamys farreri). The deduced amino acid sequence contains characteristic residues and exhibits the conserved structure of Tgfbr1 proteins. A high expression level of scallop Tgfbr1 was detected during early embryonic stages, whereas Tgfbr1 expression was enriched in the gonad and striated muscle in adults. A single nucleotide polymorphism (SNP, c. 1815C>T) in the 3' UTR was identified. Scallops with genotype TT had higher growth traits values than those with genotype CC or CT in a full-sib family, and significant differences were found between genotypes CC and TT for shell length, shell height, and striated muscle weight. An expression analysis detected significantly more Tgfbr1 transcripts in the striated muscle of scallops with genotype CC compared to those with genotype TT or CT. Further evaluation in a population also revealed higher striated muscle weight in scallops with genotype TT than those with the other two genotypes. The inverse correlation between striated muscle mass and Tgfbr1 expression is consistent with TGF-β signaling having a negative effect on cell growth.

CONCLUSION

The scallop Tgfbr1 gene was cloned and characterized, and an SNP potentially associated with both scallop growth and Tgfbr1 expression was identified. Our results suggest the negative regulation of Tgfbr1 in scallop growth and provide a candidate marker for Zhikong scallop breeding.

Low yield of genetic testing for known vascular connective tissue disorders in patients with fibromuscular dysplasia

Patients with fibromuscular dysplasia (FMD) may have clinical features consistent with Mendelian vascular connective tissue disorders. The yield of genetic testing for these disorders among patients with FMD has not been determined. A total of 216 consecutive patients with FMD were identified. Clinical characteristics were collected and genetic test results reviewed for abnormalities in the following genes: transforming growth factor-β receptor 1 and 2 (TGFβR1 and TGFβR2), collagen 3A1, fibrillin-1, smooth muscle α-actin 2, and SMAD3. A total of 63 patients (63/216; 29.2%) were referred for genetic counseling with testing performed in 35 (35/63; 55.6%). The percentage of patients with a history of arterial or aortic dissection, history of aortic aneurysm, systemic features of a connective tissue disorder, and a family history of sudden death was significantly larger in the group that underwent genetic testing (62.9% vs 18.2%, p < 0.001; 8.6% vs 1.7%, p = 0.02; 51.4% vs 17.1%, p < 0.001; and 42.9% vs 22.7%, p = 0.04, respectively). Two patients were found to have distinct variants in the TGFβR1 gene (c.611 C>T, p.Thr204lle and c.1285 T>C, p.Tyr429His). The yield of genetic testing for vascular connective tissue disorders was low in a high-risk subset of FMD patients. However, two patients with a similar phenotype had novel and distinct variants in the TGFβR1 gene, a finding which merits further investigation.

TGFBR1 signaling and breast cancer

Over the past decade mutations discovered in genes such as BRCA1, BRCA2, TP53 and PTEN, have emerged as high-penetrance susceptibility genes and are clinically relevant for determination of breast cancer risk. Genetic counseling and subsequent screening for mutations and gene rearrangement has improved patient outcome through early detection and prophylactic interventions in patients with familial breast cancer syndromes. However, these high-penetrance genes only account for a small fraction of the hereditary linked breast cancers. It is currently believed that low-penetrance susceptibility alleles and/or environmental factors may play an important role in the remaining cases. TGFBR1*6A (*6A) is a common hypomorphic variant of the type I TGF-β receptor gene (TGFBR1) that has been associated with risk for several forms of cancer, in particular breast cancer. Several epidemiological studies have suggested that patients who carry the *6A allele have an increased risk of breast cancer. Furthermore, functional analysis suggests that this mutation alters TGF-β signaling and promotes tumorigenesis. Although a decade of research has provided basic information in regards to the prevalence of this mutation in several cancer types and populations the molecular underpinning of its functional effects are poorly understood. A better understanding of the molecular mechanism of TGFBR1 signaling in breast cancer may have an impact on breast cancer risk assessment and breast cancer prevention.

Mechanisms of decreased expression of transforming growth factor-beta receptor type I at late stages of HPV16-mediated transformation

Transforming growth factor-beta (TGF-beta) signaling is disrupted in many cancers, including cervical cancer, leading to TGF-beta resistance. Although initially sensitive, human papillomavirus type 16 (HPV16) immortalized human keratinocytes (HKc/HPV16) become increasingly resistant to the growth inhibitory effects of TGF-beta during in vitro progression to a differentiation resistant phenotype (HKc/DR). We have previously shown that loss of TGF-beta sensitivity in HKc/DR is attributed to decreased expression of TGF-beta receptor type I (TGF-beta RI), while the levels of TGF-beta receptor type II (TGF-beta RII) remain unchanged. The present study explored molecular mechanisms leading to reduced TGF-beta RI expression in HKc/DR. Using TGF-beta RI and TGF-beta RII promoter reporter constructs, we determined that acute expression of the HPV16 oncogenes E6 and E7 decreased the promoter activity of TGF-beta RI and TGF-beta RII by about 50%. However, promoter activity of TGF-beta RI is decreased to a greater extent than TGF-beta RII as HKc/HPV16 progress to HKc/DR. Reduced TGF-beta RI expression in HKc/DR was found not to be linked to mutations within the TGF-beta RI promoter or to promoter methylation. Electrophoretic mobility shift and supershift assays using probes encompassing Sp1 binding sites in the TGF-beta RI promoter found no changes between HKc/HPV16 and HKc/DR in binding of the transcription factors Sp1 or Sp3 to the probes. Also, Western blots determined that protein levels of Sp1 and Sp3 remain relatively unchanged between HKc/HPV16 and HKc/DR. Overall, these results demonstrate that mutations in or hypermethylation of the TGF-beta RI promoter, along with altered levels of Sp1 or Sp3, are not responsible for the reduced expression of TGF-beta RI we observe in HKc/DR. Rather the HPV16 oncogenes E6 and E7 themselves exhibit an inhibitory effect on TGF-beta receptor promoter activity.

Structure and polymorphism analysis of transforming growth factor beta receptor 1 (TGFBR1) in pigs

Many quantitative trait loci (QTL) for growth and reproductive traits have been detected on the porcine chromosome region 1qter (SSC1qter), making it one of the most important genomic regions for pig breeding. SSC1q corresponds to human chromosome 9, on which lies transforming growth factor beta receptor 1 (TGFBR1). We cloned the porcine TGFBR1 cDNA and gene (as a candidate for QTL) and analyzed the gene structure and polymorphism. Porcine TGFBR1 consists of 9 exons and 8 introns. Intron 2 is alternatively spliced at the acceptor site, resulting in two kinds of mRNA, with putative open reading frames of 1500 and 1512 bp in length. The shorter one encodes 499 amino acid residues. The amino acid sequence has 96.2 and 97.2% sequence similarity to those of human and bovine TGFBR1, respectively. The sequence similarity between porcine and murine TGFBR1 is 95.6%. We detected three single-nucleotide substitutions in exons 1, 2, and 7. Those in exons 1 and 7 are nonsynonymous substitutions resulting in Pro8Ser and Ile413Val substitutions, respectively.

Characterization of novel transforming growth factor-beta type I receptors found in malignant pleural effusion tumor cells

Background

Tumors expressing a transforming growth factor-beta type I receptor (TβRI) mutant with sequence deletions in a nine-alanine (9A) stretch of the signal peptide are reported to be highly associated with disease progression. Expression of this mutant could interfere with endogenous TGFβ signaling in the cell. However, little is known about the importance of the remaining part of the signal peptide on the cellular function of TβRI.

Results

We cloned and identified four new in-frame deletion variants of TβRI, designated DM1 to DM4, in pleural effusion-derived tumor cells. Intriguingly, DM1 and DM2, with a small region truncated in the putative signal peptide of TβRI, had a serious defect in their protein expression compared with that of the wild-type receptor. Using serial deletion mutagenesis, we characterized a region encoded by nucleotides 16–51 as a key element controlling TβRI protein expression. Consistently, both DM1 and DM2 have this peptide deleted. Experiments using cycloheximde and MG132 further confirmed its indispensable role for the protein stability of TβRI. In contrast, truncation of the 9A-stretch itself or a region downstream to the stretch barely affected TβRI expression. However, variants lacking a region C-terminal to the stretch completely lost their capability to conduct TGFβ-induced transcriptional activation. Intriguingly, expression of DM3 in a cell sensitive to TGFβ made it significantly refractory to TGFβ-mediated growth inhibition. The effect of DM3 was to ablate the apoptotic event induced by TGFβ.

Conclusion

We identified four new transcript variants of TβRI in malignant effusion tumor cells and characterized two key elements controlling its protein stability and transcriptional activation. Expression of one of variants bestowed cancer cells with a growth advantage in the presence of TGFβ. These results highlight the potential roles of some naturally occurring TβRI variants on the promotion of tumor malignancy.

Isolation and molecular characterization of the porcine transforming growth factor beta type I receptor (TGFBR1) gene

The transforming growth factor beta (TGF beta) family is essential for normal growth and development of different organ systems. Here we describe the isolation and molecular characterization of the full-length cDNA and the determination of the genomic DNA sequence of the porcine TGFBR1 gene. The full-length TGFBR1 cDNA 1813 bp contains an open reading frame (ORF) of 1512 bp encoding a TGFBR1 protein of 503 amino acids with a calculated molecular weight (Mw) of 56.4 kDa. A BAC clone harboring the porcine TGFBR1 gene was isolated and sequenced. The results of genomic and cDNA sequences of the porcine TGFBR1 gene demonstrated that it spans a transcription unit of 62,182 bp consisting of nine exons ranging from 125 to 354 bp, and eight introns ranging from 1003 to 29,441 bp. A shorter porcine TGFBR1 isoform resulting from the alternative splicing of exon 7 in porcine TGFBR1 cDNA was detected. The shorter TGFBR1 isoform contained a 1140 bp ORF encoding 379 amino acids with a calculated Mw of 41.7 kDa. The core promoter of porcine TGFBR1 gene lacks a TATA box but contains GC boxes and CAAT boxes. Multiple transcription initiation and termination sites were identified in untranslated regions (UTR) resulting in the size of 5'-UTR varying from 15 to 62 bp, and the length of 3'-UTR varying from 169 to 228 bp. Quantitative real time PCR results showed that the TGFBR1 transcript was ubiquitously expressed in all tissues examined (i.e. fat, adrenal, brain, spinal cord, muscle, mandibular lymph node, thymus, bone marrow, uterus, spleen, testis, kidney, liver, and ovary). A total of eighty-five gene polymorphisms (77 SNPs and 8 indels) were detected in the porcine TGFBR1 gene by utilizing a panel of DNA from eight diversified pig breeds (Yorkshire, Chinese Meishan, Berkshire, Duroc, Hampshire, Landrace, Large White and Pietrain). The minor allele frequencies of these nucleotide variations varied from 0.13 to 0.5 with an average of 0.26. In addition, seventeen microsatellites were identified throughout the genomic sequence of the porcine TGFBR1 gene.

Genetic alterations of the TGF-beta signaling pathway in colorectal cancer cell lines: a novel mutation in Smad3 associated with the inactivation of TGF-beta-induced transcriptional activation

To investigate genetic alterations involved in the TGF-beta signaling pathway in colorectal cancer, we assayed DNA synthesis rates after treating TGF-beta and checked for genetic alterations in TGF-betaRII, TGF-betaRI, Smad2, Smad3, and Smad4 in 12 colorectal cancer cell lines. Eleven lines, except SNU-61, show no significant change in DNA synthesis rate after TGF-beta treatment. In these 11 lines, several mutations were found in genes involved in the TGF-beta signaling pathway: (i) frameshift deletions in the poly(A)(10) tract of the TGF-betaRII gene in SNU-407, SNU-769A, SNU-769B, and SNU-1047 cell lines, (ii) a missense mutation of Smad2 (R321Q) in SNU-81, (iii) two missense mutations in TGF-betaRI (R487W in SNU-175 and A202V in SNU-1040), and (iv) a monoallelic loss at the Smad4 locus in three cell lines. Interestingly, a missense mutation (R373H) in Smad3 gene was found in SNU-769A. To our knowledge, this is the first report of Smad3 mutation in human malignancy. This mutation was found to result in the inhibition of translocation of Smad3 protein to the nucleus and a reduction in the activity of Smad3 during TGF-beta-induced transcriptional activation. These results indicate that the majority of cell lines, which are insensitive to TGF-beta, have alterations in genes involved in the TGF-beta signaling pathway in colorectal cancer cell lines.

Novel inactivating mutations of transforming growth factor-beta type I receptor gene in head-and-neck cancer metastases

Carcinoma cell lines are frequently refractory to transforming growth factor-beta (TGF beta)-mediated cell cycle arrest. Whether and how TGF beta signaling is disrupted in the majority of human tumors, however, remains unclear. To investigate whether TGF beta signaling might be disrupted by inactivation of the key signaling molecule, the TGF beta type I (T beta R-I) receptor, and whether or not T beta R-I inactivation is associated with late stage disease, we conducted a comprehensive structural analysis of the T beta R-I gene in fine-needle aspirates of 23 head-&-neck cancer metastases. We encountered 4 different mutations of T beta R-I, 3 of which have not been previously identified. In 1 case, we found a somatic intragenic 4-bp deletion predicting for a truncation of the receptor protein. This is the first example of a true loss-of-function mutation of T beta R-I in a human epithelial neoplasm. In 2 other cases, we identified missense mutations located between the juxtamembrane- and serine-threonine kinase domains. One of these resulted in an alanine-to-threonine substitution (A230T), which disrupts receptor signaling activity by causing rapid protein degradation within the endoplasmatic reticulum. This represents a novel mechanism of inactivation of a TGF beta signaling intermediate. Finally, we identified a serine-to-tyrosine substitution at codon 387 (S387Y) in a metastasis but not in the corresponding primary tumor. We had previously shown this S387Y mutant to be predominantly associated with breast cancer metastases and to have a diminished ability to mediate TGF beta-dependent signaling. In aggregate, these findings provide further support for the hypothesis that inactivation of the TGF beta signaling pathway occurs in a significant subset of human cancers.

Analysis of TGF-beta type I receptor for mutations and polymorphisms in head and neck cancers

Transforming growth factor-beta receptor (TbetaR)-dependent signals are critical for cell growth and differentiation and are often disrupted during tumorigenesis. The entire coding region of TbetaR-I and flanking intron sequences from 30 head and neck carcinomas were examined for alterations using "Cold" SSCP and direct sequencing. No somatic point mutations were found in the TbetaR-I gene. In contrast, 14 polymorphic sequence changes were detected in TbetaR-I in 13 (43%) of the samples, including eight (27%) nucleotide alterations identified as polymorphisms in an exon-1 (GCG)(9) microsatellite repeat, a previously reported tumor susceptibility allele. A nine base pair deletion was found in 23% of the samples including five heterozygous and two homozygous deletions as well as single homozygous 12bp deletion. Additionally, six heterozygous polymorphisms in intronic sequences were determined, including one heterozygous C/A genotype at the +82 nucleotide position of the intron-5 intervening sequence (IVS), and five heterozygous G/A genotypes within intron-7 at the +24 nucleotide position. Exon-1 polymorphisms in the (GCG)(9) microsatellite region of the TbetaR-I gene and their association with head/neck cancers, suggest that development of these cancers may be a direct consequence of loss of responsiveness to TGF-beta mediated growth inhibition.

The chromosome 9q genes TGFBR1, TSC1, and ZNF189 are rarely mutated in bladder cancer

This study assessed a series of bladder tumours and bladder tumour cell lines for sequence variation in the Krüppel-like zinc finger gene ZNF189, the tuberous sclerosis complex gene 1 (TSC1), and the TGF beta receptor type I (TGFBR1). All three genes have been mapped to 9q regions commonly deleted in transitional cell carcinoma of the bladder. Mutation analysis of the coding sequence of these genes revealed several variant bands that were shown to represent polymorphisms. Mutation analysis of the ZNF189 gene in bladder cancer cell lines identified one amino acid substitution (lysine-->isoleucine) at position 323 in exon 4. For the TSC1 gene, two mutations were identified in two out of 27 independent cell lines. Both mutations result in a truncated protein. Furthermore, one out of 36 bladder tumours had a frameshift mutation in exon 7 of the TSC1 gene. No tumour-specific mutations were found in the TGFBR1 gene. The length of the polyalanine tract present in exon 1 of the TGFBR1 gene was also investigated. It has been suggested that the allele with six alanines (6A) is more frequent in patients with bladder and other cancers, so bladder cancer patients were compared with normal controls. In both groups, the percentage of heterozygotes was 17%. These data do not support a role for the 6A allele in bladder cancer susceptibility.

Alternative splicing within the TGF-beta type I receptor gene (ALK-5) generates two major functional isoforms in vascular smooth muscle cells

We have identified in rat vascular smooth muscle cells (SMCs) the simultaneous expression of two TGF-beta type I receptor (ALK-5) cDNAs, occurring as a consequence of alternate usage of AG splice acceptor motifs separated by 12 nucleotides located at an intron-exon junction. When translated the resultant full length proteins differ from each other only by the in-frame presence or absence of Gly-Pro-Phe-Ser residues adjacent to their transmembrane domain. Stable expression of these alternate ALK-5 isoforms in ALK-5-deficient cells demonstrated that both were competent in signaling TGF-beta-induced growth inhibition and gene transcription, but with an apparently distinct potency. Our data suggest that alternate splicing within the ALK-5 gene is an important mechanism whereby SMCs may regulate their response to TGF-beta.

A Deletion in the Gene for Transforming Growth Factor β Type I Receptor Abolishes Growth Regulation by Transforming Growth Factor β in a Cutaneous T-Cell Lymphoma

Spontaneous regression of skin lesions is characteristic of lymphomatoid papulosis (LyP), a clonal cutaneous lymphoproliferative disorder. A minority of LyP patients progress to anaplastic large cell lymphoma (ALCL) in which skin lesions no longer regress and extracutaneous dissemination often occurs. In 1 such case, we developed a tumor cell line, JK cells, and show that these cells are resistant to the growth inhibitory effects of transforming growth factor β (TGF-β) due to the loss of cell surface expression of the TGF-β type I receptor (TβR-I). Reverse transcriptase-polymerase chain reaction (RT-PCR) and sequencing of JK cell TβR-I cDNA clones identified a deletion that spanned the last 178 bp of exon 1, including the initiating methionine. Hybridization of a radiolabeled fragment internal to the deletion was detected in the genomes of TGF-β–responsive cells, but not in JK cells, indicating that they contain no wild-type TβR-I gene. PCR primers that flanked the deleted TβR-I region amplified a single band from JK cell genomic DNA that lacked the last 178 bp of exon 1 and all of the ≈ 5 kb of intron 1. This JK cell-specific genomic TβR-I PCR product was distinct from products amplified from TGF-β–responsive cells and was also readily detected in tumor biopsies obtained before the establishment of the JK cell line. Our results identify the first inactivating mutation in TβR-I gene in a human lymphoma that renders it insensitive to growth inhibition by TGF-β.

Two target regions of allelic loss on chromosome 9 in urinary-bladder cancer

Allelic losses on chromosome 9 are common in a wide variety of human tumors; moreover, two predisposing loci for some inherited cancer syndromes, i.e., familial malignant melanoma and Gorlin syndrome, have been identified on this chromosome. To define the location of putative tumor suppressor genes involved in cancer of the urinary bladder, 85 bladder cancers were examined for allelic loss at 18 microsatellite loci on chromosome 9. Correlations were also sought between loss of heterozygosity on chromosome 9 and several clinicopathological parameters. Allelic loss was observed in 54 of the tumors (64%) and deletion mapping identified two target regions; one at an interval on 9p21 flanked by D9S736 and D9S165, and the other at an interval on 9q31-34 flanked by D9S58 and D9S61. No subtle mutation was detected in the PTCH gene which lies in the latter interval. Allelic loss on chromosome 9 was observed frequently in low grade and non-invasive tumors as well as in tumors of more advanced phenotype. Inactivation of tumor suppressor genes lying in either of two regions of common deletion identified on chromosome 9 might affect carcinogenic mechanisms at an early stage of tumor development in the urinary bladder.

Brachydactyly type B: clinical description, genetic mapping to chromosome 9q, and evidence for a shared ancestral mutation

Autosomal dominant brachydactyly type B (BDB) is characterized by nail aplasia with rudimentary or absent distal and middle phalanges. We describe two unrelated families with BDB. One family is English; the other family is Canadian but of English ancestry. We assigned the BDB locus in the Canadian family to an 18-cM interval on 9q, using linkage analysis (LOD score 3.5 at recombination fraction [theta] 0, for marker D9S938). Markers across this interval also cosegregated with the BDB phenotype in the English family (LOD score 2.1 at straight theta=0, for marker D9S277). Within this defined interval is a smaller (7.5-cM) region that contains 10 contiguous markers whose disease-associated haplotype is shared by the two families. This latter result suggests a common founder among families of English descent that are affected with BDB.

Cloning and characterization of a naturally occurring soluble form of TGF-beta type I receptor

Transforming growth factor-beta1 (TGF-beta1) has been implicated to play an important role both in the process of normal development and in the pathogenesis of a wide variety of disease processes, including those of the kidney. TGF-beta1 regulates diverse cellular functions via a heteromeric signaling complex of two transmembrane serine/threonine kinase receptors (types I and II). Several distinct type I receptors have been described and are thought to determine specificity of the TGF-beta response and confer multifunctionality. This report reveals the cloning of a novel, naturally occurring soluble form of TGF-beta type I receptor, designated sTbetaR-I, from a rat kidney cDNA library. In vivo expression of a mRNA transcript encoding the sTbetaR-I, which lacks the transmembrane and cytoplasmic domains, is confirmed by RT-PCR followed by Southern blot analysis and by RNase protection assay. The sTbetaR-I mRNA abundance is greater in the neonatal rat kidney compared with the adult rat kidney. Furthermore, sTbetaR-I is a functional protein capable of binding TGF-beta1 ligands in the presence of a TGF-beta type II receptor on the cell surface, as determined by affinity cross-linking with 125I-labeled TGF-beta1. Studies using p3TP-Lux reporter construct reveal that this novel protein may function as a potentiator of TGF-beta signaling. The discovery of a sTbetaR-I provides an additional level of complexity to the TGF-beta receptor system.