REGULAR ARTICLES

hKAP1.6 and hKAP1.7, Two Novel Human High SulfurKeratin-Associated Proteins are Expressed in the Hair FollicleCortex

Yutaka Shimomura, Noriaki Aoki, Michael A. Rogers,² Lutz Langbein,* JuÈrgen Schweizer,² and Masaaki ItoDepartment of Dermatology, Niigata University School of Medicine, Niigata, Japan; *Divisions of Cell Biology and ²Biochemistry of Tissue Speci®c

Regulation, German Cancer Research Center, Heidelberg, Germany

Hair ®ber differentiation involves the expression ofboth hair keratin intermediate ®lament proteins andtheir associated proteins, termed keratin-associatedproteins. In this study, cDNA clones encoding twonovel keratin-associated proteins were isolated fromhuman hair follicle mRNA. The predicted aminoacid sequence derived from these clones revealedthat these proteins represent members of the humankeratin-associated protein 1 family. They showstrong sequence homology to two previously

described keratin-associated protein 1 family mem-bers hKAP1.1 A and hKAP1.1B. We have calledthese new proteins hKAP1.6 and hKAP1.7, respec-tively. RNA in situ hybridization studies of humananagen hair follicles using a conserved probe forthese four keratin-associated protein 1 membersdemonstrated the expression of this group in the dif-ferentiated portions of the hair cortex. Key words:human gene/in situ hybridization/keratin/keratin-associ-ated protein. J Invest Dermatol 118:226±231, 2002

Hair is a strongly keratinized tissue formed within thehair follicle. The hair ®ber possesses severaldistinctive morphologic features, among which arean external cuticular sheath, an inner cortical region,and, occasionally, a narrow, central lying medulla.

The major structural proteins of hair are the keratin intermediate®lament proteins, whose 8 nm ®laments form the rigid hair shaftthrough crosslinking of these ®laments with their associatedproteins (KAPs) (Powell and Rogers, 1997). More than 60 hairKAPs have been found in various species and they have beenclassi®ed into proteins exhibiting high sulfur (16±30 mol%cysteine, KAP1±KAP3, KAP10±KAP16 families) (Swart andHaylett, 1973; Swart et al, 1976; Powell et al, 1983; Frenkel et al,1989; Zhumbaeva et al, 1992; Huh et al, 1994; Powell and Rogers,1997; Aoki et al, 1998; Cole and Reeves, 1998; Mitsui et al, 1998;Takaishi et al, 1998; Kuhn et al, 1999; Rogers et al, 2001), ultra-high sulfur (>30% cysteine; KAP4, KAP5, KAP9, and KAP17families) (McNab et al, 1989; MacKinnon et al, 1990; Fratini et al,1994; Jenkins and Powell, 1994; Powell et al, 1995; Perez et al,1999; Rogers et al, 2001), and high glycine/tyrosine (KAP6±KAP8families) amino acid content (Kuczek and Rogers, 1987; Fratiniet al, 1993; Aoki et al, 1997). Furthermore, these KAPs have beensubdivided into a total of 17 families (KAP1.n±KAP17.n) based onan initial proposal by Rogers and Powell (1993). This nomen-clature is based on their cysteine/tyrosine-glycine content, as wellas the degree of amino acid homology within each family and thenature of the repeat structures often found in these molecules(McNab et al, 1989; Huh et al, 1994; Aoki et al, 1998; Cole andReeves, 1998; Takaishi et al, 1998; Kuhn et al, 1999). So far genes

encoding KAPs have been isolated from humans, sheep, rabbit, rat,and mouse (Wood et al, 1990; Fratini et al, 1993; Powell et al, 1995;Aoki et al, 1997). In humans, six KAP1 genes and ®ve KAP5 geneshave been published (MacKinnon et al, 1990; Zhumbaeva et al,1992; Emonet et al, 1997; Perez et al, 1999; Rogers et al, 2001).

We have isolated two cDNAs encoding new members of thehuman KAP1 family, hKAP1.6 and hKAP1.7, found during theanalysis of the hKAP1.1 A/B genes in patients possessing acongenital fragile hair disorder (for a description of thehKAP1.1 A/B genes and their nomenclature, see Discussion). Inthis study, we have characterized these novel KAP1 members andexamined their expression in the hair follicle.

MATERIALS AND METHODS

Isolation of the KAP1 genes Peripheral leukocyte DNAs wereprepared from healthy individuals using standard protocols. The humanhKAP1 A/B and hKAP1.6 genes were ampli®ed by polymerase chainreaction (PCR) using human genomic DNAs as templates andhKAP1.1 A/B-speci®c oligonucleotide primers (KAP1.5¢-1, 5¢-ACT-TATAAAAAGCCGGCAGTGG-3¢; and KAP1.3¢-1, 5¢- GGTACT-GGAGTTCAGAAGATTG-3¢) (Zhumbaeva et al, 1992). PCR wasperformed using KOD-Plus-DNA polymerase (Toyobo, Tokyo, Japan).Ampli®cation conditions were 94°C for 2 min, followed by 35 cycles of94°C for 15 s, 53°C for 30 s, and 68°C for 1 min, with a ®nal extensionat 68°C for 7 min. The ampli®ed fragments were analyzed on a 6%polyacrylamide gel. After extraction of the fragments from the gel, direct¯uorescent chain termination DNA cycle sequencing of the PCRproducts was performed (Big Dye DNA sequencing kit, AppliedBiosystems, Foster City, CA). The DNA sequences were analyzed on anABI373 DNA sequencer (Applied Biosystems). The resulting sequenceswere used to search for DNA homologies with genes registered in theGenBank/EMBO/DDBJ databases using the BLASTN program.

Reverse transcription (RT) PCR Total RNA was isolated using anIsogen kit (Nippongene, Tokyo, Japan) from 15 freshly plucked anagenhair follicles according to the manufacturer's recommendations. Theresulting RNA was reverse transcribed using an oligo(dT) primer and

0022-202X/02/$15.00 ´ Copyright # 2002 by The Society for Investigative Dermatology, Inc.

226

Manuscript received March 13, 2001; revised August 6, 2001; acceptedfor publication October 15, 2001.

Reprint requests to: Dr. Noriaki Aoki, Department of Dermatology,Niigata University School of Medicine, Asahimachi-dori, Niigata 951-8510, Japan. Email: yshimo@med.niigata-u.ac.jp

Abbreviation: KAP, keratin-associated protein.

was preceded by 10 min digestion with RNase-free DNase (Roche,Mannheim, Germany) in order to ensure the removal of contaminatinggenomic DNA. The cDNAs were ampli®ed by PCR using the sameprimers and with the same PCR conditions as described above. ThePCR products were directly sequenced after gel puri®cation.

3¢-RACE To identify the sequence of the 3¢-noncoding region inhKAP1.6 mRNA, 3¢-RACE was performed using a standard 3¢-RACEkit according to the manufacturer's instructions (Takara, Tokyo, Japan).After the synthesis of the ®rst strand cDNAs using an oligo(dT)-adaptorprimer derived from total RNA of anagen hair follicles, the 3¢-cDNAend of hKAP1.6 was ampli®ed by PCR using the adaptor primer (5¢-GTTTCCCAGTCACGAC-3¢) and internal gene-speci®c primer(KAP1.5¢-4, 5¢-TTCAGATTCAACTCCTGACACC-3¢) derived fromthe 5¢-noncoding region of the partial hKAP1.6 cDNA. The ampli®edcDNA fragments were directly sequenced after extraction from the gel.

Human scalp library screening The preparation and arraying of acDNA library from human scalp tissue has been described previously(Rogers et al, 1995; 2001). A PCR product speci®c for the 3¢-noncodingregion of the hKAP1.1 A/B gene (Zhumbaeva et al, 1992) was preparedby ampli®cation of genomic DNA (upper primer, 5¢-CCATGG-CCTGCTGTCAGAC-3¢; lower primer, 5¢-GTGGCTGTGTGA-TGAGAGGTTG-3¢). The hKAP1.1 A/B PCR product was randomlylabeled with 32P-dCTP (Amersham-Pharmacia-Biotech, Bucks, U.K.)and used as a probe in order to screen the human scalp cDNA libraryaccording to methods described previously (Rogers et al, 1995). Brie¯y,the hybridization was performed overnight at 65°C using a hybridizationsolution containing 6 3 sodium citrate/chloride buffer (SSC), 0.1%sodium pyrophosphate, 5 3 Denhardt's solution, 1% sodium dodecylsulfate (SDS), and 1 3 106 cpm per ml of the radiolabeled probe.Thereafter, multiple washings were performed with 0.5 3 SSC/1% SDSat 65°C, and the ®lters were autoradiographed overnight using KodakAR5 ®lm. The screening resulted in many positive clones. Twenty ofthese clones were analyzed.

In situ hybridization of human scalp tissue The in situ hybridizationprotocol with human scalp cryostat sections using hybridization probesderived from cloned 3¢-noncoding region probes of keratin and KAPgenes has been described previously (Rogers et al, 1997; Langbein et al,1999). In these experiments, the 130 bp PCR product used for thehuman scalp cDNA library screening was cloned into the plasmidpCR2.1 (TA cloning kit, Invitrogen, GroÈningen, Netherlands). Thisconstruct was used to generate a 35S cRNA transcript of hKAP1.1 A/B.The bright ®eld microscopy and In situ hybridization signals werevisualized using a confocal laser scanning microscope (LSM510, CarlZeiss, Jena/Oberkochen, Germany). The instrument allows thesimultaneous visualization of the re¯ected light from epi-illumination forthe detection of hybridization signals (red channel) and transmitted lightin bright ®eld (green channel). The two channels were combined by anoverlay in pseudocolors (transmission image in green, electronicallychanged into black/white; re¯ection image, i.e., hybridization signals, inred).

Accession numbers The hKAP1.6, and hKAP1.7 sequences areavailable under the accession numbers AB052868, AB055057in theEMBL/GenBank/DDBJ databases.

RESULTS

Isolation of human KAP1.6 and KAP1.7 cDNAs In anattempt to analyze the sequences of human KAP1 genes, weampli®ed the hKAP1.1 A/B genes from human genomic DNA byPCR using primers derived from the original DNA sequence(Zhumbaeva et al, 1992). The result of polyacrylamide gelelectrophoresis showed the presence of two DNA fragments(Fig 1A). The direct DNA sequencing of these products indicatedthat the 700 bp PCR product corresponded to the hKAP1.1 A/Bgenes and that the 550 bp product might be a putative novel KAP1gene. Therefore, RT-PCR was performed using total RNAextracted from plucked human hair follicles in order to con®rm theexpression of these putative genes at the mRNA level. Care wasneeded in the analysis of the PCR products because KAP genes, ingeneral, consist of only one exon, thus making the discriminationbetween PCR products from true cDNA and contaminatinggenomic DNA dif®cult. Therefore, predigestion of human scalpRNA with DNase I was performed, as well as the ampli®cation of a

multiple exon containing housekeeping gene, in order to ensurethe speci®city of the RT-PCR reaction. This experiment alsodetected two cDNA products, 700 bp and 550 bp in size (Fig 1B).The sequence of each cDNA was completely consistent with thatof the hKAP1.1 A/B genes or the novel gene, indicating that thesegenes are not pseudogenes and are actually expressed in the humanhair follicle. In order to isolate the 3¢-end of these cDNAs, wedeveloped a 2-fold strategy. First, we ampli®ed human hair folliclecDNAs using a 3¢-RACE strategy, and obtained two cDNAfragments corresponding to hKAP1.1 A/B and the novel gene viaPCR ampli®cation (data not shown). DNA sequencing of theshorter fragment allowed the construction of a full-length cDNA ofthe novel gene (Fig 2A), and we have termed this gene hKAP1.6for reasons explained below. In addition, we also attempted toisolate the hKAP1.6 cDNA by screening of a human scalp cDNAlibrary with a hKAP1.1 A/B 3¢-noncoding region probe, on theassumption that the high sequence identity of the originallyidenti®ed hKAP1.1 A/B and hKAP1.6 PCR products mightextend into their 3¢-noncoding region. Although the analysis of 20cDNA clones failed to lead to the discovery of the hKAP1.6cDNA, it resulted in the identi®cation of a further, weaklyexpressed, new member of the hKAP1 family, termed hKAP1.7(Fig 2B).

Figure 1. hKAP1.6 gene and its mRNA can be detected in thehuman genome and in hair follicle mRNA. (A) PCR ampli®cationof the hKAP1.1 A/B and hKAP1.6 genes in three individuals (lanes 1±3). (B) RT-PCR ampli®cation of hKAP1.1 A/B and hKAP1.6 mRNAsfrom human hair follicles (lane 1). GAPDH mRNA, 597 bp in size, wasampli®ed as a control using two primers located, respectively, in exon 3and exon 7 of GAPDH gene. A genomic fragment of GAPDH, 1101 bpin size, was not detected (lane 3). PCR without reverse transcription didnot detect any products (lanes 2, 4), indicating that there was nogenomic DNA contamination in this experiment. RT(+)/RT(±) denotecontrols with or without reverse transcription. MMW, molecular weightmarker.

VOL. 118, NO. 2 FEBRUARY 2002 IDENTIFICATION OF hKAP1.6 AND hKAP1.7 227

Characterization of hKAP1.6 and hKAP1.7 Comparisonsbetween hKAP1.1 A/B, hKAP1.6, and hKAP1.7 not only showedhigh nucleotide sequence identity in their coding regions, but alsocomplete sequence identity in their 3¢-noncoding regions. Thishigh degree of identity was also seen in the 5¢-noncoding region ofhKAP1.1 A/B and hKAP1.6. Translation of the open readingframe of hKAP1.6 yielded a protein of 131 residues with acalculated molecular weight of 13.6 kDa (Fig 2A). The cysteineand serine content of this protein was high, i.e., 24% and 15%,respectively. In the deduced amino acid sequence, the pentapeptiderepeat C(C/Y)Q(p/T)S appeared four times, and a similarsequence, CCETS, appeared once (Fig 2A). In contrast, thededuced hKAP1.7 protein consisted of 85 amino acid residues witha molecular mass of 9.1 kDa, and also had a high cysteine (26%) andserine (13%) content (Fig 2B). In this amino acid sequence thedouble cysteine containing pentapeptide CCQTS could be foundonly once. In addition, hKAP1.6 and hKAP1.7 had further variantsof these double cysteine containing pentapeptides in their C-

terminal region. Database searching for homologous proteinsequences revealed that hKAP1.6 and hKAP1.7 shared a highidentity with members of the sheep, rat, and human KAP1 family(Fig 3). In particular, the degree of identity between hKAP1.1 A/B, hKAP1.6, and hKAP1.7 was striking. Comparison ofhKAP1.1 A/B and hKAP1.6 revealed one amino acid changebetween the proteins as well as a 46 residue deletion in the aminoterminal region of hKAP1.6. Similarly, comparison betweenhKAP1.1 A/B and hKAP1.7 revealed complete identity betweenthe proteins, but with a 92 residue amino acid deletion inhKAP1.7.

In situ hybridization analysis using a common probe tohKAP1.1 A/B, hKAP1.6, and hKAP1.7 In order todetermine the region of mRNA expression of hKAP1.1 A/B,hKAP1.6, and hKAP1.7, we analyzed hair follicles from humanscalp biopsies by means of in situ hybridization. Due to the highsequence identity between hKAP1.1 A/B, hKAP1.6, andhKAP1.7 it was not possible to create in situ hybridization probesspeci®c for any single family member. The probe used in thesestudies therefore recognized all four members presented here. Inlongitudinal sections of anagen hair follicles, mRNA transcriptswere exclusively detected predominantly in the highlydifferentiated portions of the uppermost cortex region (Fig 4A).At higher magni®cations, no signal could be detected in the hairshaft cuticle cells (Fig 4B). Moreover, no mRNA expression forthese genes was found in the hair ®ber medulla (Fig 4C). Inaddition, no expression was observed in the hair follicle inner rootsheath or outer root sheath (Fig 4A±C) or the interfollicularepidermis, sebaceous glands or sweat glands (data not shown).

DISCUSSION

In this study, we identi®ed two cDNAs encoding the novel humanKAPs, hKAP1.6 and hKAP1.7. In 1993, Rogers and Powellproposed a modi®cation of the nomenclature used to classify KAPsand termed a group of sheep and human high sulfur KAP proteinsfound to be expressed in the cortical layer of the hair follicle theKAP1 family (Rogers and Powell, 1993). To date, eight membersof the KAP1 family have been reported from sheep, rabbit, andhumans (Elleman and Dopheide, 1972; Powell et al, 1983;Zhumbaeva et al, 1992; Mitsui et al, 1998), and four additionalhuman members have been described in a recent report (Rogerset al, 2001). In humans, two KAP1 family genes were originallyidenti®ed and termed hB2A and hB2B (Zhumbaeva et al, 1992). Inkeeping with the newer nomenclature, these genes were renamedhKAP1.1 A and hKAP1.2 (Rogers et al, 2001). In addition, recentevidence arose showing another identical copy of the hKAP1.1 Agene present on a separate human gene locus. This gene has beendesignated hKAP1.1B (Rogers et al, 2001).

Like the KAP1 members described previously, the newhKAP1.6 and hKAP1.7 proteins had a high cysteine residuecontent and showed signi®cant homology with all of the knownKAP1 family members, especially the two initially described humanmembers. The multialignment of the members of the human,sheep, and rat KAP1 family revealed that most of these proteins canbe divided into ®ve individual domains: an N-terminal domain, arepetitive I domain, a central nonrepetitive domain, a repetitive IIdomain, and a C-terminal domain (Fig 3). The N-terminal, centralnonrepetitive, and repetitive II domains appear to be highlyconserved in all three species, which could indicate that they playan essential role in the function of the KAP1 family. This isstrikingly seen in the hKAP1.7 protein, which contains these threedomains but does not have the multiple double cysteine containingamino terminal repeat structure seen in the other proteins isolatedthus far. In contrast, the C-terminal domain is the smallest regionfound, consisting of 3±18 residues, and is conserved to a lesserdegree in the three species analyzed. This region, however, showshigh similarity within each respective species. One further regionthat is striking among the KAP1 family members is the repetitive Idomain, with its large degree of repetitiveness and size variability.

Figure 2. Nucleotide sequence of hKAP1.6 and hKAP1.7, and thededuced amino acid sequence of the protein products. (A)hKAP1.6; (B) hKAP1.7. Nucleotides are numbered consecutively at theleft-hand side. The derived amino acid sequence appears below thenucleotide sequence and the pentapeptide repeats are boxed.Polyadenylation signal is underlined. The accession numbers for therespective nucleotide sequences are: hKAP1.6, AB052868; hKAP1.7,AB055057.

228 SHIMOMURA ET AL THE JOURNAL OF INVESTIGATIVE DERMATOLOGY

Figure 4. A probe common to hKAP1.1 A/B, hKAP1.6, and hKAP1.7 hybridizes tomRNA transcripts present in the cortex ofthe hair follicle. Due to the high DNA sequencehomology of these genes, the in situ probe used inthis experiment recognizes all four transcripts. (A)Longitudinal hair follicle section; (B) highermagni®cation of (A); (C) longitudinal section of ahair follicle possessing a medulla. The red arrowsdemarcate the area of major KAP expression.Note the lack of inner root sheath (B) andmedulla (C) labeling. ors, outer root sheath; irs,inner root sheath; co, cortex; dp, dermal papilla;med, medulla, hcu, cuticle of the hair shaft; icu,cuticle of the inner root sheath. Scale bar: 150 mm.

Figure 3. The predicted amino acidsequences of hKAP1.6 and hKAP1.7 andmultialignment of KAP1 family members.Residues that are identical are colored light blue.Dashes denote gaps in the sequence to maximizealignment. The pentapeptide repeats are boxedusing blue lines. Brackets show the ®ve KAPsubdomains. Note that the N-terminal domain ofhKAP1.6 is boxed with a red line. The accessionnumbers for the respective human, rat, and sheepprotein sequences are: hKAP1.1 A (hB2A),X63337; hKAP1.1B (AC007455, nt 8801±9334);hKAP1.2 (hB2B), X63338; sB2A, kr2a_sheep.sw;sB2B, kr2b_sheep.sw; sB2C, kr2c_sheep.sw:sB2D, kr2d_sheep.sw; rB2E and rB2F, AB003753.

VOL. 118, NO. 2 FEBRUARY 2002 IDENTIFICATION OF hKAP1.6 AND hKAP1.7 229

Decapeptide repeat structures have been previously reported in theKAP1 family members of sheep and rat (Powell et al, 1983; Mitsuiet al, 1998), and fundamentally appeared to be composed of twopentapeptide subelements. These elements are CCQPT and SIQTSin sheep, and CCQP(S/T) and C(S/T)QSS in rat. In human, theyconsist essentially of amino acid variations of a double cysteine-containing pentapeptide, CCQ(p/T)S and CCETS. Therefore, likethe C-terminal domain, a certain degree of sequence repeatspeci®city is present in individual species. In addition, thecomparisons of KAP1 members in the respective species showedexclusively high homologies at the N-terminal, central non-repetitive, repetitive II, and C-terminal domains in all species,indicating that the distinctions among individual KAP1 members inthe same species might be dependent upon the number ofpentapeptide repeats in the repetitive I domain. Therefore, therepetitive I domain may decide the individual functional charac-teristics of KAP1 members in a speci®c species, and may participatein species-speci®c interactions with the C-terminal domain of otherKAP1 family members. Interestingly, hKAP1.1 A/B and hKAP1.2have another unique amino acid sequence (consensus sequence,FCGFPS(F/C)ST(G/S)GTC(D/G)SS) inserted into the repetitive Iregion of these proteins. This sequence cannot be detected in therepetitive I domains of rat and sheep KAP1 members alreadyreported.

The analysis of amino acid multialignment of KAP1 memberscould not provide convincing evidence for the presence oforthologous proteins among the three species. Recently four newmembers of the KAP1 family (hKAP1.1B, hKAP1.3, hKAP1.4,hKAP1.5), possessing DNA sequences unique to hKAP1.6 andhKAP1.7 as well as to the other previously described human KAP1family members (Zhumbaeva et al, 1992), were identi®ed on thehuman genome and cDNA sequences for three of these genescould be found (Rogers et al, 2001). An orthologous relationship ofthese sequences to that of the KAP1 family members in sheep andrat could also not be found in these studies. Therefore, at present itis uncertain whether there are identi®able orthologs of sheep andrat KAP1 members in the human genome. In addition, it is dif®cultto decide whether one human KAP1 member corresponds to amember in another species because not all of the KAP1 familymembers in any one species have yet been found. Due to this lackof orthologous relationships between species, the decision taken inthe naming of the two new KAP1 family members was basedexclusively on what was, as yet, known in humans (Zhumbaevaet al, 1992; Rogers et al, 2001). Therefore, we have termed thenovel KAP1 members identi®ed in this study hKAP1.6 andhKAP1.7.

The in situ hybridization performed here showed the cumulativeexpression of the transcripts of hKAP1.1 A/B, hKAP1.6, andhKAP1.7 exclusively in the differentiated portion of the hair folliclecortex, which was consistent with the previous reports on sheep andrat KAP1 family members (Powell et al, 1991; Mitsui et al, 1998).This is also consistent with recent data showing expression ofhKAP1.5 in the human hair follicle cortex (Rogers et al, 2001). Itmust also be kept in mind, however, that due to the high homologyoccurring between these four gene sequences, the probe used for thein situ hybridization cannot differentiate between members.Therefore probable quantitative differences among the individualmembers cannot be distinguished. Moreover, if there wereindividual differences in the initiation and termination of mRNAsynthesis, this would also not be detected. In any case, the isolation ofboth a speci®c RT-PCR product of hKAP1.6 from human scalpmRNA and a clone from a human scalp cDNA library for hKAP1.7point to the expression of these genes in human scalp. The presenceof only one hKAP1.7 transcript in the 20 cDNA clones isolated andthe absence of an hKAP1.6 transcript indicate low expression levelsof these two genes compared to hKAP1.1 A/B.

Mutations in the hair keratin genes hHb1 and hHb6 havepreviously been shown to be present in patients suffering from thecongenital hair disease monilethrix, which is characterized bybeaded and fragile hairs (Winter et al, 1997a, b; Korge et al, 1999).

In an attempt to ®nd a causal mutation in a family of patients withfragile, but not moniliform, hairs, we analyzed all type II hairkeratin genes, including hHb1 and hHb6, of these patients, anddetected no pathogenic mutations. As KAPs have also beenpostulated as playing a role in hereditary hair genodermatoses, wedecided to analyze these putative candidate genes, which eventuallyled to the discovery of the new KAP1 family members presentedhere. We could not detect mutations in either the hKAP1.1 A/Bor hKAP1.6 genes of the patients analyzed, however. Morerecently, it has been reported that transgenic mice overexpressingHoxc 13 in differentiating keratinocytes of hair follicles developedalopecia and several KAP genes were downregulated in postnatalskin of these mice (Tkatchenko et al, 2001). Thus, the productionof transgenic mice expressing a mutated form of the KAPs isprobably more likely to provide insight into its function in the hairfollicles, and may represent a putative model for a human hairdisorder in the future. Furthermore, the discovery of the completeset of human KAP gene, of which hKAP1.6 and hKAP1.7 are apart, should advance our knowledge concerning the characteristicsof hair between individuals as well as the role of KAPs in hereditaryhair diseases.

We wish to thank Claudia Ehmann and Silka Praetzel for their technical expertise.

We also wish to thank Dr. Herbert Spring for his help with confocal laser microscopy.

The arrayed human scalp cDNA library used in this report is available from the

German Human Genome Resource Center (see http://www.rzpd.de). The library

number is p636. Likewise the clone hKAP1.7, which was isolated from this library, is

available there under the number DKFZp636L2317Q4. We wish to thank the

members of the RZPD for their continuing support. Part of this work was supported by

the German Research Council under the number SCHW539/4-1.

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