Characterization of the human forkhead gene FREAC-4. Evidence for regulation by Wilms' tumor suppressor gene (WT-1) and p53

The multisystemic functions of FOXD1 in development and disease

Transcription factors (TFs) participate in a wide range of cellular processes due to their inherent function as essential regulatory proteins. Their dysfunction has been linked to numerous human diseases. The forkhead box (FOX) family of TFs belongs to the "winged helix" superfamily, consisting of proteins sharing a related winged helix-turn-helix DNA-binding motif. FOX genes have been extensively present during vertebrates and invertebrates' evolution, participating in numerous molecular cascades and biological functions, such as embryonic development and organogenesis, cell cycle regulation, metabolism control, stem cell niche maintenance, signal transduction, and many others. FOXD1, a forkhead TF, has been related to different key biological processes such as kidney and retina development and embryo implantation. FOXD1 dysfunction has been linked to different pathologies, thereby constituting a diagnostic biomarker and a promising target for future therapies. This paper aims to present, for the first time, a comprehensive review of FOXD1's role in mouse development and human disease. Molecular, structural, and functional aspects of FOXD1 are presented in light of physiological and pathogenic conditions, including its role in human disease aetiology, such as cancer and recurrent pregnancy loss. Taken together, the information given here should enable a better understanding of FOXD1 function for basic science researchers and clinicians.

Smad6s regulates plasminogen activator inhibitor-1 through a protein kinase C-beta-dependent up-regulation of transforming growth factor-beta

Plasminogen activator inhibitor-1 (PAI-1) is a serpin class protease inhibitor that plays a central role in the regulation of vascular function and tissue remodeling by modulating thrombosis, inflammation, and the extracellular matrix. A central mediator controlling PAI-1 is transforming growth factor-beta (TGF-beta), which induces its expression and promotes fibrosis. We have found that a unique member of the Smad family of signal transduction molecules, Smad6s, modulates the expression of PAI-1. Overexpression of Smad6s in endothelial cells increases promoter activity and PAI-1 secretion, and an antisense to Smad6s suppresses the induction of PAI-1 by TGF-beta. The effect of Smad6s on the PAI-1 promoter appeared to be the result of increase binding of the forkhead winged helix factor FoxD1 to a TGF-beta-responsive element. Furthermore, the effect of Smad6s on PAI-1 up-regulation and on FoxD1 binding was found to result from up-regulation of TGF-beta and could be inhibited by the blocking TGF-beta signaling with Smad7. The ability of Smad6s to regulate the TGF-beta promoter and subsequent PAI-1 induction was suppressed by a selective protein kinase C-beta (PKC-beta) inhibitor. Consistent with the in vitro data, we found that increased Smad6s in diseased vessels correlated with increased TGF-beta and PAI-1 levels. Overall, our results demonstrate that the level of Smad6s can alter the level of TGF-beta and the subsequent induction of PAI-1 via a FoxD1 transcription site. Furthermore, our data suggest that this process, which is up-regulated in diseased vessels, can be modulated by the inhibition of PKC-beta.

Characterization of the human renal Na(+)-sulphate cotransporter gene ( NAS1) promoter

Sulphate (SO(4)(2-)) plays an essential role during growth, development, and cellular metabolism. Recently, we have isolated the human renal Na(+)-SO(4)(2-) cotransporter (hNaSi-1) that is implicated in the regulation of serum SO(4)(2-) levels. To gain an insight into hNaSi-1 regulation, our aims were to clone and characterize functionally the hNaSi-1 gene ( NAS1) promoter. We PCR-amplified 3742 bp of the NAS1 5'-flanking region, which is 64% AT-rich and contains numerous putative cis-acting elements. The NAS1 transcription start site was mapped to 25 bp upstream from the translation start site. NAS1 promoter truncations fused to luciferase gene constructs transfected into renal LLC-PK1, MDCK and OK cells allowed us to establish that the first 169 bp of the NAS1 promoter are sufficient for basal transcription. Furthermore, the NAS1 promoter conferred responsiveness to the polycyclic aromatic hydrocarbon 3-methylcholanthrene (3-MC), but not to thyroid hormone (T(3)) or vitamin D [1,25-(OH)(2)D(3)]. Site-directed mutagenesis of the NAS1 promoter identified a functional xenobiotic response element at -2,052, which conferred 3-MC responsiveness. The human NAS1 gene promoter is not responsive to Vitamin D or T(3), unlike the mouse Nas1 promoter with which it shares approximately 40% sequence similarity, but is transactivated by 3-MC, suggesting that the control of renal SO(4)(2-) reabsorption via the regulation of NAS1 transcription may be important for maintaining the sulphation potential for kidney polycyclic aromatic hydrocarbon metabolism.

A winged helix forkhead (FOXD2) tunes sensitivity to cAMP in T lymphocytes through regulation of cAMP-dependent protein kinase RIalpha

Forkhead/winged helix (FOX) transcription factors are essential for control of the cell cycle and metabolism. Here, we show that spleens from Mf2-/- (FOXD2-/-) mice have reduced mRNA (50%) and protein (35%) levels of the RIalpha subunit of the cAMP-dependent protein kinase. In T cells from Mf2-/- mice, reduced levels of RIalpha translates functionally into approximately 2-fold less sensitivity to cAMP-mediated inhibition of proliferation triggered through the T cell receptor-CD3 complex. In Jurkat T cells, FOXD2 overexpression increased the endogenous levels of RIalpha through induction of the RIalpha1b promoter. FOXD2 overexpression also increased the sensitivity of the promoter to cAMP. Finally, co-expression experiments demonstrated that protein kinase Balpha/Akt1 work together with FOXD2 to induce the RIalpha1b promoter (10-fold) and increase endogenous RIalpha protein levels further. Taken together, our data indicate that FOXD2 is a physiological regulator of the RIalpha1b promoter in vivo working synergistically with protein kinase B to induce cAMP-dependent protein kinase RIalpha expression, which increases cAMP sensitivity and sets the threshold for cAMP-mediated negative modulation of T cell activation.

An amphioxus winged helix/forkhead gene, AmphiFoxD: insights into vertebrate neural crest evolution

During amphioxus development, the neural plate is bordered by cells expressing many genes with homologs involved in vertebrate neural crest induction. However, these amphioxus cells evidently lack additional genetic programs for the cell delaminations, migrations, and differentiations characterizing definitive vertebrate neural crest. We characterize an amphioxus winged helix/forkhead gene (AmphiFoxD) closely related to vertebrate FoxD genes. Phylogenetic analysis indicates that the AmphiFoxD is basal to vertebrate FoxD1, FoxD2, FoxD3, FoxD4, and FoxD5. One of these vertebrate genes (FoxD3) consistently marks neural crest during development. Early in amphioxus development, AmphiFoxD is expressed medially in the anterior neural plate as well as in axial (notochordal) and paraxial mesoderm; later, the gene is expressed in the somites, notochord, cerebral vesicle (diencephalon), and hindgut endoderm. However, there is never any expression in cells bordering the neural plate. We speculate that an AmphiFoxD homolog in the common ancestor of amphioxus and vertebrates was involved in histogenic processes in the mesoderm (evagination and delamination of the somites and notochord); then, in the early vertebrates, descendant paralogs of this gene began functioning in the presumptive neural crest bordering the neural plate to help make possible the delaminations and cell migrations that characterize definitive vertebrate neural crest.

Mechanisms of FOXC2- and FOXD1-mediated regulation of the RI alpha subunit of cAMP-dependent protein kinase include release of transcriptional repression and activation by protein kinase B alpha and cAMP

We have reported recently that mice overexpressing the forkhead/winged helix transcription factor FOXC2 are lean and show increased responsiveness to insulin due to sensitization of the beta-adrenergic cAMP-PKA(+) pathway and increased levels of the RI alpha subunit of cAMP-dependent protein kinase (PKA) (Cederberg, A., Grønning, L. M., Ahren, B., Taskén, K., Carlsson, P., and Enerbäck, S. (2001) Cell 106, 563-573). In this present study, we reveal that FOXC2 and a related factor, FOXD1, specifically activate the 1b promoter of the RI alpha gene in adipocytes and testicular Sertoli cells, respectively. By deletional mapping, we discovered two different mechanisms by which the Fox proteins activated expression from the RI alpha 1b promoter. In 3T3-L1 adipocytes, an upstream region represses promoter activity under basal conditions. Bandshift experiments indicate that overexpression of FOXC2 promotes the release of a potential repressor from this region. In Sertoli cells, sequences downstream of the transcription start sites mediate the activating effect of FOXD1, and protein kinase B alpha/Akt1 strongly induces this effect. Furthermore, we show that an inactive FOXD1 mutant lowers the cAMP-mediated induction of the RI alpha 1b reporter construct. In summary, winged helix transcription factors of the FOXC/FOXD families function as regulators of the RI alpha subunit of PKA and may integrate hormonal signals acting through protein kinase B and cAMP in a cell-specific manner.

WT1 proteins: functions in growth and differentiation

The Wilms' tumor 1 gene (WT1) has been identified as a tumor suppressor gene involved in the etiology of Wilms' tumor. Approximately 10% of all Wilms' tumors carry mutations in the WT1 gene. Alterations in the WT1 gene have also been observed in other tumor types, such as leukemia, mesothelioma and desmoplastic small round cell tumor. Dependent on the tumor type, WT1 proteins might either function as tumor suppressor proteins or as survival factors. Mutations in the WT1 gene can also result in congenital abnormalities as observed in Denys-Drash and Frasier syndrome patients. Mouse models have proven the critical importance of WT1 expression for the development of several organs, including the kidneys, the gonads and the spleen. The WT1 proteins seem to perform two main functions. They regulate the transcription of a variety of target genes and may be involved in post-transcriptional processing of RNA. The WT1 gene encodes at least 24 protein forms. These isoforms have partially distinct biological functions and effects, which in many cases are also specific for the model system in which WT1 is studied. This review discusses the molecular mechanisms by which the various WT1 isoforms exert their functions in normal development and how alterations in WT1 may lead to developmental abnormalities and tumor growth.

Activation of Vitamin D Receptor by the Wilms' Tumor GeneProduct Mediates Apoptosis of Renal Cells

Abstract. The Wilms' tumor transcription factor WT1 is required for kidney development, but little is known about WT1 downstream signaling in renal cells. This study reported an approximately fivefold upregulation of vitamin D receptor (VDR) mRNA and protein in human embryonic kidney (HEK) 293 cells that stably expressed WT1 at a level comparable to the developing kidney in vivo. Co-transfection of HEK 293 cells with expression plasmids encoding four different WT1 splicing variants stimulated mouse vdr promoter activity more than fourfold. A 201-bp fragment was identified in the proximal vdr promoter that was required for transactivation by WT1. This critical sequence contained a predicted WT1 consensus site, which bound to recombinant WT1 protein. Temporal changes of vdr and wt1 mRNA levels in developing rat kidneys were correlated closely. The active metabolite 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) strongly inhibited the proliferation of wt1-transfected HEK 293 cells. Exposure to 1,25-(OH)2D3 caused apoptosis of cultured wt1 immunopositive cells from mouse embryonic kidney cortex. These findings suggest that transcriptional activation of the VDR by WT1 can mediate programmed death of renal embryonic cells in response to 1,25-(OH)2D3. The results provide the first evidence for a role of the vitamin D endocrine system in renal cell growth and differentiation during development.

Molecular aspects of renal tubular handling and regulation of inorganic sulfate

The renal proximal tubular reabsorption of sulfate plays an important role in the maintenance of sulfate homeostasis. Two different renal sulfate transport systems have been identified and characterized at the molecular level in the past few years: NaSi-1 and Sat-1. NaSi-1 belongs to a Na(+)-coupled transporter family comprising the Na(+)-dicarboxylate transporters and the recently characterized SUT1 sulfate transporter. NaSi-1 is a Na(+)-sulfate cotransporter located exclusively in the brush border membrane of renal proximal tubular and ileal cells. Recently, NaSi-1 was shown to be regulated at the protein and mRNA level by a number of factors, such as vitamin D, dietary sulfate, glucocorticoids and thyroid hormones, which are known to modulate sulfate reabsorption in vivo. The second member of renal sulfate transporters, denoted Sat-1, belongs to a family of Na+-independent sulfate transporter family comprising the DTDST, DRA and PDS genes. Sat-1 is a sulfate/bicarbonate-oxalate exchanger located at the basolateral membrane of proximal tubular epithelial cells and canalicular surface of hepatic cells. Contrary to NaSi-1, no physiological factor has been found to date to regulate Sat-1 gene expression. Both NaSi-1 and Sat-1 transporter activities are implicated in pathophysiological states such as heavy metal intoxication and chronic renal failure. This review focuses on recent developments in the molecular characterization of NaSi-1 and Sat-1 and the mechanisms involved in their regulation.

The mouse Na(+)-sulfate cotransporter gene Nas1. Cloning, tissue distribution, gene structure, chromosomal assignment, and transcriptional regulation by vitamin D

NaSi-1 is a Na(+)-sulfate cotransporter expressed on the apical membrane of the renal proximal tubule and plays an important role in sulfate reabsorption. To understand the molecular mechanisms that mediate the regulation of NaSi-1, we have isolated and characterized the mouse NaSi-1 cDNA (mNaSi-1), gene (Nas1), and promoter region and determined Nas1 chromosomal localization. The mNaSi-1 cDNA encodes a protein of 594 amino acids with 13 putative transmembrane segments, inducing high affinity Na(+)-dependent transport of sulfate in Xenopus oocytes. Three different mNaSi-1 transcripts derived from alternative polyadenylation and splicing were identified in kidney and intestine. The Nas1 gene is a single copy gene comprising 15 exons spread over 75 kilobase pairs that maps to mouse chromosome 6. Transcription initiation occurs from a single site, 29 base pairs downstream to a TATA box-like sequence. The promoter is AT-rich (61%), contains a number of well characterized cis-acting elements, and can drive basal transcriptional activity in opossum kidney cells but not in COS-1 or NIH3T3 cells. We demonstrated that 1,25-dihydroxyvitamin D(3) stimulated the transcriptional activity of the Nas1 promoter in transiently transfected opossum kidney cells. This study represents the first characterization of the genomic organization of a Na(+)-sulfate cotransporter gene. It also provides the basis for a detailed analysis of Nas1 gene regulation and the tools required for assessing Nas1 role in sulfate homeostasis using targeted gene manipulation in mice.

Minimal phenotype of mice homozygous for a null mutation in the forkhead/winged helix gene, Mf2

Mf2 (mesoderm/mesenchyme forkhead 2) encodes a forkhead/winged helix transcription factor expressed in numerous tissues of the mouse embryo, including paraxial mesoderm, somites, branchial arches, vibrissae, developing central nervous system, and developing kidney. We have generated mice homozygous for a null mutation in the Mf2 gene (Mf2(lacZ)) to examine its role during embryonic development. The lacZ allele also allows monitoring of Mf2 gene expression. Homozygous null mutants are viable and fertile and have no major developmental defects. Some mutants show renal abnormalities, including kidney hypoplasia and hydroureter, but the penetrance of this phenotype is only 40% or lower, depending on the genetic background. These data suggest that Mf2 can play a unique role in kidney development, but there is functional redundancy in this organ and other tissues with other forkhead/winged helix genes.

Analysis of K-ras, N-ras, H-ras, and p53 in lung neuroendocrine neoplasms

This study screened 11 samples of typical carcinoid (TC), 4 samples of atypical carcinoid (AC), 1 sample of large cell neuroendocrine carcinoma (LCNEC), and four metastases for point mutations in exons 5 to 8 of the p53 gene, and exons 1 and 2 of the K-ras. H-ras, and N-ras genes using polymerase chain reaction (PCR)-single-strand conformation polymorphism (SSCP) and direct sequencing and by immunohistochemistry for p53. Exon 1 of K-ras was mutated in two samples of low-grade AC and a metastasis from one of these tumors (GAT12 and AGT12, respectively). No mutations in N-ras or H-ras were found. Mutations in exons 5 and 8 of the p53 gene were identified in a high-grade AC and a LCNEC. Positive immunostaining for p53 was present in three samples, with only one genotypic mutation shown (LCNEC). In conclusion, point mutations of the p53 gene were infrequent in these pulmonary neuroendocrine tumors, did not correlate in all samples with immunostaining, and were associated with the higher-grade tumors. Second, the presence of K-ras mutations seems to be associated with the higher-grade carcinomas. Third, N-ras and H-ras mutations were not found with these pulmonary neuroendocrine tumors.

The kidney-expressed winged helix transcription factor FREAC-4 is regulated by Ets-1. A possible role in kidney development

In this paper we show that the kidney-expressed winged helix transcription factor FREAC-4 is regulated by Ets-1, another kidney-expressed transcription factor. Through transfection experiments three Ets-1 cis-elements are identified within the first 152 nucleotides upstream of the transcription start in the freac-4 promoter. These sites are confirmed in a DNase I in vitro protection assay using recombinant Ets-1 protein. In cotransfection experiments using an Ets-1 expression vector, the induction of freac-4 reporter gene activity is attenuated approximately 6-fold when the three Ets-1 binding sites are mutated. Furthermore, we demonstrate that overexpression of Ets-1 in the human embryonic kidney cell line 293 is sufficient to increase freac-4 mRNA levels. These results are compatible with the hypothesis that Ets-1 acts as an upstream regulator of FREAC-4 expression during kidney development.

The two-exon gene of the human forkhead transcription factor FREAC-2 (FKHL6) is located at 6p25.3

The gene for the human transcription factor forkhead related activator 2 (FREAC-2; HGMW-approved symbol FKHL6) has been characterized and found to consist of two exons separated by an intron of 3.6 kb. The first exon encodes the forkhead DNA-binding domain and one of the transcriptional activation domains, AD2. The second exon contains the coding sequence corresponding to the C-terminal activation domain AD1. The full-length FREAC-2 protein is predicted to be 444 amino acids, which adds 39 amino acids to the previously published partial cDNA sequence. A 2-kb CG island is centered around the 5' end of the FREAC-2 gene. Fluorescence in situ hybridization was used to localize the human FREAC-2 gene to chromosomal position 6p24-p25, and the localization was further refined by radiation hybrid mapping to 6p25.3.

FREAC-1 contains a cell-type-specific transcriptional activation domain and is expressed in epithelial-mesenchymal interfaces

The forkhead transcription factor FREAC-1 is a potent transcriptional activator. We have localized a transcriptional activation domain in the C-terminus of FREAC-1 and another one to a stretch of approximately 60 amino acids in the central part of the protein. While the C-terminal activation domain activates in all cell lines tested, the activation domain in the central part of the protein is functional only in cell lines derived from lung. This cell-type-specific activity is retained when the activation domain is fused to the heterologous DNA binding domain of Gal4. The human FREAC-1 gene was found to consist of two exons separated by an intron of 1.2 kb. Exon 1 encodes the forkhead DNA binding domain and the cell-type-specific activation domain. Exon 2 encodes the general activation domain. The distribution of FREAC-1 expression during embryogenesis was investigated by in situ hybridization. FREAC-1 mRNA was found in mesenchyme in immediate proximity to endodermal epithelia throughout the digestive, urinary, and respiratory tracts. Mesenchyme surrounding the notochord and adjacent to the ectodermal epithelia of the oral cavity and developing teeth also expresses FREAC-1. The pattern of FREAC-1 expression, with highest levels in the mesenchyme next to the epithelium and gradually diminishing as the distance from the epithelium increases, suggests that FREAC-1 expression is a response to epithelial paracrine signaling and that FREAC-1 may play a role in epitheliomesenchymal interactions.

Mouse HNF-3/fork head homolog-1-like gene: structure, chromosomal location, and expression in adult and embryonic kidney

Screening of a mouse kidney cDNA library with a HNF-3/fork head domain probe revealed cDNA Hfh-1L containing the highly conserved fork head DNA-binding domain. The Hfh1L cDNA shows 92.7% homology at the nucleic acid level with the fork head gene HFH-1 from rat. Southern blot analyses demonstrated that the Hfh-1L gene is highly conserved in a wide variety of species, including goldfish and frog. Sequencing the corresponding genomic clone, we found that the Hfh-1L gene is most likely intronless. By interspecific back-cross analysis, the Hfh-1L gene was localized to mouse chromosome 13. In order to analyze the expression pattern of Hfh-1L, we performed Northern blot analyses and revealed a 2.7-kb transcript in adult kidney and stomach. In situ hybridization experiments of adult mouse kidney showed Hfh-1L expression in the outer medulla of the kidney and the transitional epithelium. In light of the significance of a number of fork head genes in early embryonic development, the pattern of expression during murine embryogenesis was examined by reverse transcriptase-polymerase chain reaction (RT-PCR), and Hfh-1L transcripts were detected in mouse embryos at every stage tested from day 10.5 to 16.5 postconception (p.c.) and in the developing metanephros of 14.5- and 15.5-day p.c. embryos. This expression pattern suggests that the Hfh-1L gene is involved in the development of the kidney.

A human forkhead/winged-helix transcription factor expressed in developing pulmonary and renal epithelium

Members of the forkhead/winged-helix transcription factor family play crucial roles during vertebrate development. A human hepatocyte nuclear factor/forkhead homolog (HFH)-4 cDNA encoding a 421-amino acid protein was isolated from a human fetal lung cDNA library. By Southern blot analysis of human-rodent somatic cell hybrid genomic DNA, the human HFH-4 gene localizes to chromosome 17q23-qter. This is the locus of another forkhead/winged-helix gene, the interleukin enhancer binding factor gene. RNA blot analysis revealed a 2.5-kilobase human HFH-4 transcript in fetal lung, kidney, and brain as well as in adult reproductive tissues, lung, and brain. By in situ hybridization, HFH-4 expression is associated with differentiation of the proximal pulmonary epithelium, starting during the pseudoglandular stage of human lung development. During human renal morphogenesis, HFH-4 is expressed in the developing epithelial cells of the ureteric duct, glomerulus, and epithelial vesicles. The unique pattern of HFH-4 expression during human fetal development suggests a role for this forkhead/winged-helix factor during pulmonary and renal epithelial development.

Mouse Mesenchyme forkhead 2 (Mf2): expression, DNA binding and induction by sonic hedgehog during somitogenesis

Cloning and sequencing of mouse Mf2 (mesoderm/mesenchyme forkhead 2) cDNAs revealed an open reading frame encoding a putative protein of 492 amino acids which, after in vitro translation, binds to a DNA consensus sequence. Mf2 is expressed at high levels in the ventral region of newly formed somites, in sclerotomal derivatives, in lateral plate and cephalic mesoderm and in the first and second branchial arches. Other regions of mesodermal expression include the developing tongue, meninges, nose, whiskers, kidney, genital tubercule and limb joints. In the nervous system Mf2 is transcribed in restricted regions of the mid- and forebrain. In several tissues, including the early somite, Mf2 is expressed in cell populations adjacent to regions expressing sonic hedgehog (Shh) and in explant cultures of presomitic mesoderm Mf2 is induced by Shh secreted by COS cells. These results suggest that Mf2, like other murine forkhead genes, has multiple roles in embryogenesis, possibly mediating the response of cells to signaling molecules such as SHH.

Cloning and characterization of freac-9 (FKHL17), a novel kidney-expressed human forkhead gene that maps to chromosome 1p32-p34

We describe the cloning of a near full-length cDNA of 4258 nucleotides encoding freac-9 (HGMW-approved symbol FKHL17), a novel human forkhead gene. The 5' untranslated region is unusual since it is very long, 2127 nucleotides, and contains 15 upstream AUG codons. Hybridization to a panel consisting of RNA derived from 50 different tissues showed that freac-9 is transcribed exclusively in the kidney. The kidney-derived cell lines COS-7 and 293 are shown to express freac-9. A combination of fluorescence in situ hybridization and somatic cell hybrids localizes freac-9 to the chromosomal region of 1p32-p34. The conceptual translation product predicts a protein of 372 amino acids with an N-terminal domain rich in acidic amino acids and with a high likelihood of forming an amphipatic helix, a DNA binding forkhead domain, and a C-terminal region that has a high probability of forming an amphipatic beta-sheet. The amino acid sequence of the DNA binding forkhead motif of FREAC-9 is identical to that of another forkhead protein, FREAC-4, whereas 12 substitutions are present at the nucleotide level. There are no similarities in regions outside of the DNA binding domains of FREAC-9 and FREAC-4 and since freac-4 maps to a different chromosome (5q12-q13) it is likely that an evolutionary selection has acted to maintain identical DNA binding domains between these two kidney expressed transcription factors.

Chromosome localization, sequence analysis, and expression pattern identify FKHL 18 as a novel human forkhead gene

The forkhead gene family of transcription factors belongs to the "winged helix" class of DNA-binding proteins. Today over 40 members of this gene family have been identified. Forkhead genes have been shown to be involved in embryonic development, tumorigenesis, and direction of tissue specificity of gene expression. Here we describe a new human forkhead gene called freac-10 (HGMW-approved symbol FKHL 18). A combination of fluorescence in situ hybridization and somatic cell hybrids localizes freac-10 to the chromosomal region of 20q11.1-q11.2. Hybridization to a panel consisting of RNA derived from 50 different tissues shows that freac-10 is transcribed predominantly in the aorta, thus having a unique expression pattern compared with other forkhead genes. Sequence comparison reveals a striking similarity, over the conserved DNA binding region, to a murine forkhead gene-fkh-3. We propose, based on sequence differences in the N- and C-terminal regions of the forkhead domain and a clear difference in expression pattern between freac-10 and fkh-3, that freac-10 represents a novel member of this gene family.