The 5-HT2 serotonin receptor gene Htr-2 is tightly linked to Es-10 on mouse chromosome 14

11,231-234

GENOMICS

(1991)

SHORT COMMUNICATION The 5-HT2 Serotonin Receptor Gene Htr-2 Is Tightly Linked to Es-l 0 on Mouse Chromosome 14 JIAN LIU,* YAN CHEN,*

CHRISTINE A. Kozw, t AND LEI Yu*

*Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana 46202; and tLaboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892 Received

February

7, 1991;

The neurotransmitter serotonin (&hydroxytryptamine, 5-HT) is involved in diverse physiological effects in the central and peripheral nervous systems and in smooth muscle (Sanders-Bush, 1988; Fozard, 1989; Richardson and Engel, 1986). Serotonin exerts its effects by interaction with specific membrane receptors classified into pharmacologically distinct subtypes (Bradley et al., 1986; Hoyer, 1988; Peroutka, 1988). A number of receptor subtypes have been cloned at either the cDNA or the genomic DNA level, including the 5-HTiA (Kobilka et al., 1987; Fargin et al., 1988), 5-HT,c (Ltibbert et aZ., 1987; Julius et al., 1988; Yu et aZ., 1991), and 5-HT, (Pritchett et al., 1988; Julius et al., 1990) receptors. The gene for the ~-HT,A receptor has been mapped to human chromosome 5 at q11.2-q13 (Kobilka et al., 1987) and that for the 5-HT,c receptor has been localized to the X chromosome in mouse (Yu et al., 1991). Here we report the chromosomal mapping of the 5-HT, receptor gene to mouse Chr 14. DNA made from the rat brain cDNA libraries (Snutch et aZ., 1990) was used as template in polymerase chain reaction (Saiki et aZ., 1988) with two degenerate oligonucleotide primers designed from data

May

16, 1991

published sequences of serotonin receptor genes (Liibbert et al., 1987; Julius et al, 1988; Pritchett et al., 1988; Julius et al., 1990; Kobilka et aZ., 1987). The PCR products were cloned in Ml3 vectors and sequenced by the method of dideoxy chain termination (Sanger et al., 1977). A subcloned PCR fragment corresponding to part of the 5-HT, receptor gene (Julius et aZ., 1990; Pritchett et al., 1988) was used to isolate several cDNA clones from the libraries. Plasmids were excised from the phage vector XZAPII (Stratagene) by helper phage rescue, and the cDNA inserts were subcloned into Ml3 vector for sequence determination. The cDNA sequence and deduced amino acid sequence are shown in Fig. 1. There have been two previous reports of the molecular cloning of this receptor from the rat brain (Pritchett et aZ., 1988; Julius et aZ., 1990), but they differ in a single nucleotide that alters the reading frame, resulting in different deduced amino acid sequences in the amino terminal region. Our sequencing data agree with those of Julius et al. (1990). The 5-HT, receptor is a G protein-coupled membrane receptor and displays the paradigmatic profile of seven hydrophobic domains, a common feature of most G protein-coupled membrane receptors (Ovchinnikov, 1982; O’Dowd et al., 1989; Hartig, 1989). An interesting aspect of the 5-HT, receptor is that it contains a leucine zipper structure (Struhl, 1989; Vinson et al., 1989; Busch and Sassone-Corsi, 1990) within the hydrophobic domain I (Fig. 1). Leutine zippers have been found in a number of DNAbinding proteins that serve as transcription regulators and are hypothesized to play a crucial role in dimer formation of these proteins for the proteinDNA interaction (Struhl, 1989; Vinson et al., 1989; Busch and Sassone-Corsi, 1990). Since the 5-HT, receptor is a membrane-bound protein and does not

Clones coding for the 5-HT, serotonin receptor were isolated from rat brain cDNA libraries. Using one of the cDNA clones as the probe, mouse genomic DNAs from intersubspecific backcrosses were analyzed by Southern blot hybridization for a restriction fragment length polymorphism. The 5-HT, serotonin receptor gene, Rtr-2, was mapped to mouse Chromosome 14 and is closely linked with the marker Es-l 0. o 1991 Academic POW, IW.

Sequence EMBL/GenBank

revised

from this article have been deposited with the Data Libraries under Accession No. M64667. 231

OSSS-7543/91$3.00 Copyright D 1991 by Academic Press, Inc. All rights of reproduction in any form reserved.

1200

-380

-370

l’-ITCTGhTGG

CTCAACTCTT

-320

-310

-420 CTGCCTTCCC

-410 CTCCTCGTTT

-400 WhTCTChTG

-390 CTGll-TThhC

-360 GGMGCAGCA

-350 ThTTChhCCC

-340 GhGhhTThGc

-330 TGMhGhn-I

TChCCCGhTh

ChMhCl-rTT

-260 hhCTGCl’-TTT

-250 l’7-ICCCCTl-I

-200

-300 ~cc~.uc

-290 CAGGAACACG

-280 ~GTGTCCC

-270 CGAATACTCA

-240 GC~CCGTGA

-230 GM”TAC,,G

-220 CTCAGCCGTG

-210 GGCTCTCCCT

-180

-170

-160

MTCh&MG

CA'R2,CACl-I

-120 AGCC,,C&CAT -60 GCCCAWCTA

-50 TGhcccccTh

I-E

GCC

Al.

TAC Tyr

1260 AAG

I."

-190

CA0

GM

CAT

GCT

GAG

Cl"

Glu hsp Al.

-100 TCAGCACGTC

-90 CTAGCCCCAG

-SO GGCACGhAGh

TGMTGGTG*

-40 GTCTCTCChC

-30 *CTrchTCTG

-20 CTACMCTTC

cGccTT*G*C

((*t

Gl"

11s LmJ cy,

*TG I(st

60 chh Gl”

GGT my

CAT Asp

30 TCT

AAT

ATC

CTG

AGC

TCh

Al-I

GlU **p

*,n w

11s ser La"

s.r

s.r

CTC Lau

90 MT *ml

CCC GlY

75 CCG pro

hGG *rg

TAC Tyr

CAT HIS

GAC **p

-70

-10

45 CCh

GM

m

Gl"

Lys As" Irp N

Tw

GGA

AAT

ATA

CTC

TCT

GCT

IT*

scr

Ala

Leu Iru *

285 GTC

ATC

ATG

Ile

nar

ATG “et

345 TCA Sar

e Leu "01 . ACC Thhr

330 MC han

TAT Tyr

TTC Pha 390 G-E

CTG Leu

TCC

An:

CCT

"al

net

Pro "al

Ser net. hu

435 AGC

AAG

CTC

GCG

ser Lys Lau cy* *I.

GCh

*CA

AGT

GTC

GTG

255 ATT

TTh

I19 PI0 *sn

ser

lau

‘lTC Phe

105 ffih *rg

CAT Asp

ATT

CTC

ATG

ITA

CTT Lau

GCC Ala

ACC

405 ATC

TCC ssr

*cc

ATT

270 GCT

300 TCC

CTA

AAG

3:5 CTG

hhh

Lys l.ys Le" Cl"

CAG

AhT

AmI Ala

ATA

CCT

360 GAT Asp

ATG tit.

CTG Lau

3;5 =ITC pha

110 Ala

TAC

420 CGG

CTG

TAT

GW

CW Lett

‘KG

WT Gly

CC-T

ITG

CTT I&u

CC-I

Al-I

CTG

TW

Trp IL

GCC

ATC

1.590 1.650 TAAGTAACTT

TAC

465 GhT

GTG

CTC

Tyr Lea h‘p

va1 La"

CTG

TAT Tyr

TCT

480 hCG

Pha 9-r

Thr

GCh Ala

TCC SW

GCC Ala

*TC

CM:

MC

540 CCC

Ila

Gln hsn Pro

I-I-T

ATG

110 "at AII

495 CAC

CTC

TGC

His IAU Cys Ala 555 WC

I1e 9~

Leu hsp 570 ACC

CCC hrg

Val

CAC

AGC

TCC

AGA

Ii*=

scr *rg

Ph* ha"

9.r

AZ.9 Thr Ly.

CCC Ala

TTC m*

cn: La”

600 TGG

ACC

ATA

GTA

615 GGT

ATA

TCC

630 ATC

CCA

GTC

TCI

CAT Asp

GAT Asp

TCG Se=

705 GTT

CTC

Val

Leu Ila

ACC

ThC

660 MC Lys

GTC “al

TTT ehe

ATG

Gly I1e Se= "et AAG Lys

GAG Glu

675 GGG Gly

AGC Ser

720 hTh

765 TIC

AM

525 GTC

CAC

Val Trp Thr I1e Ser "al

MC

GhC

110 Hi* GTG

ITC

510 TCC

WA

Pro 110 Pro ".I TGC Cys

CTG La”

CTC

AGC

*CT

hTC

MC

780 TO,

GTT

C&G

AAh

GM

ACT

825 CGA

CCC

AAh

CT*

CCC

CTG

TCA

GM

AAG

CTC

885 TIC

CM

CGG

1.930

1.910 hrrrr#AhT

1.920 GlTChChhGh

1.930 ccGcT&xhT

1.940 TIocluhTT

1.970

1.98G ThhhnrrhT

1.990 2GGhIhhmc

1,950 TcrwrrhhT

1,960 lmchGhm

2,010 CITCTACITC

2.020 lTGGGGlTT*

2,070 CTmhhAG

2.080 ThTChhMGh

2.090 ThhlTCCACT

2.110 CuxTGra

2,130 AATMACAGC

2.140 hTwnxhGG

2.150 TclwGGrhh

2.170

2.050

2.200

2,210

GcccnTGhG

cAGmhcchG

ThGhMGhGT

2.250 TrTcrwcrG

2.260 TWXAGTAG

2.270 CXTClThGGC

2.310 TlUGhGrIh

2.320 Tchwmhhh

2.330 GTGhXlllT

ITT

WA

645 CTA

2.370 MMGhhTGc

2.380 IKiCCTChCG

-T

2,430 AGGCATCATG

2.440 GTGCACGGCT

2,450 GTCTCIhhTC

2,490 ChGGMlTCh

GTCAI-TCTCA

GCC

2.390

GAT

GAC

MC

Asp Asp Am, Phe 750 ATG

GTG

hTC

"et

"al

I1e

TGT

GTG

910 Thr Isu

TTC

CTC

TTG

Ser

CAG

TCT

2,510 GC-ATC

2.730 cMcTThhm

GGTTGTTATG

2,750 AhhhhhGThT

GMThGhlTC

CITMCTGAT

2.810 TCAGAMAGG

GCCTGThTCh

CATTCTTCCT

CCC

Ser ThC

2,aso

GAG

Chh

Gin Lys Ala

GCG

Cys Ly., "al

ATC

TGC

TGC

1020 T-E

*TC

*CC

"et

Trp cys Pro Phe Phe ,le

~t,r

1005 TTC

TGC

1035 1050 1065 ATG WC GTC ATC TGC hhh Ghh TCC TGC AhT GM MT GTC AK net Ala va1 Ile cys Lys GlU scr cys A*" GlU AS” “al Il.2

hhG

GTG

1080 WA CCC Gly

Ala

2.520

2.690 TTCTAGCATA

3.160 3.150 ThChGGGTh.4 MTGCTGAAA

"al

2.470

2,670 2,680 GGATCTCATO hGKGhGChG

3.110 AGGACACTCT

Phe Phe Leu Phe "al

2.460

2,630 hhhhcGcGtI

TIAATCCACC

Val

CCA

*CT

Cl"

CC*

2.410 AmxGGsGh

2,620 *TThllTGTh

2.610 hEThTTTh’C

3,090 CCAGCTGMG

GTA

2.300 GhcnTGhTh

2.a

2,570 MThhhThTh

ACCAGTTACC

CTG

2.290 hhhh2.35G GGhMTMaG

2,550 2,560 TCGTGTCTCC MhCThhhTh

3,030 hhhhGChhhT

990 I-K

cc-

2.240

2.340

lmT*TGhGG

TTCCCTCAAA

TTC

855 CCT

hGT

Cys Val

2.500

2.980 TTCTTCTTCC

GTG

2.200 ThlTrmGrh

2.230

2.420 hmmT&wG

'ITT

2,970 ThhhhChhTh

ATC

2.220

2.1lo GmGGuTcc

Ph. Gly Lau Gln

2.920 ATGCATAGM

CCC

l.mcl

rlmrrwrh

2,910 hTTGChCCch

975 CTG

AAT ATC Am Ile

1.900 CA’CAGA’IZCC

hlnnchrr

2.870 2,860 CATATITGCC AAGCCMCAA

AAT

1.740 hhhmhGGrh

1.170 hcrEshhT

I19 *la CM:

1.690

1.96G TchTrGhhhT

prmmcl

AGC

1.520

1.850 GrhhThTMT

960 MG

Ser h‘"

L-x Gly Ile

1.940 *,,,‘Z’ThTTG

2,790 CGATTTCTTT

Gln Ser Ila

Gly Lys

1,790 MITCACGAC

GAG

ATG Het

GTT

1,730 htTmhThIh

Glu Pro Gly Ser Tyr

ACG Tk

‘ITT

1.680 GGCTGGCUT

AGA

930 AGG AI&

945 ATC

1.670

*rg

CGA *I&

GGG

I."

1.630 AATGAGGGAT

ATACGMCCT

"is

WC Gly

CTG

1,570 ThcGhmxr

1,660 CThrrCTChh

915 'KC

ATC

AC4

Ikr

1,560 crhGG&lm 1.620 GIwMm

Phe Leu Pro Gin ser

XC

CrT

Ul

1.510

1.610 TrGGccrrrT

900 ChC

GCA Ala

XC

1,6OG

Pha 6.x

Pha Gin hrg Sar Ilc

ICC S.r

TCTAMACCA

ser

Ser SeT Glu Lys Lu PKC

CAG

1.540 ATGTGCTCM:

TTC

LU

TGC Cy#

1.490

1.480

840 TCC

hGC

GAC A.p

l

ATI

795 GCC hla

*CC

1290 LAG

1350 AM

Ila

TCT I T T GTG GCh T T T ITC ATC CCC CT* ACC ATC Gly Ser Phs "a, Ala Phe phs IIe Pro ,a" Thr Ile CTG

AM

1335 Al0 kt

ATC

GGC

ASP Leu ser Thr AT6 All, Lys Leu Ala PKC 870 TCA

690 GCC *la

GGA

CAC

AT*

1320 GIT

GAT A.p

cn:

hCT

TM II*

CAG

5.55 AM Ly.

735

Thr Tyr Phe Leu Thr 11s Lys Ser Lcu Gin Lys Glu PKC GAC

CTT Leu

1275 CAG

hhC

A‘"

TCh

V.,

CTC

‘XG Val

9.1 au

ACA

CAG

1230 II*

119 Ia"

AAC

Glu Gln z

AGT

ATT

Gly Gin Lys Lys *.n

1,720

2.190 ATC

IT*

Ser Gln La" Gin Val

GTGhCrrhl7

CCC

Lau Tyyr Gly Tyr Are Trp Pro Leu Pro

450 ATC

1,530 ACCMCTATA

1.890

GM

Gl"

Thr Ila

Ile

va1

GTMTATGAC

GTG

ChG

ThThCCGhTG MC

.

GTC

TGT

240 lm

cys

1,470

150 135 120 ~r.x MC ACT TCG GAA GCh TCO MC TGG ACA ATT GAT GCT GM MC AGA ACC MC *,a *sn Thhr s*r GlU Ah ser Am *rp mr lb Asp *la GlU *ml *rg Thr Am N N N N 210 195 180 165 CTC TCC TGT GM GGG TC CTC 03. CCG AU TGC CTC TCC ATT Cl-T CAT CTC CAG La,J se= cy, GlU Gly Tyr Leu Pm Pt.0 Thr cys Ia" s*r Ile La" His Lsu Gin 225 MC

CTG

Lys Pro L.u Gln L.u

1365 1300 1395 Chh CAG TCG Ghh GAG MT T G T ACA GAC MT AR GM AGC OKi MT Ghh MC GIT Cl" Gin Ser Cl" Glu Am, Cy. Thr ASP Mn Il* Glu ,%w V.1 h‘m Glu Ly. Vd Y cK2 1410 1.426 1,430 1.440 1.45G 1.460 AGC TGT GTG TGA TGM CTGGhTGCTh II XCMTTGC ( :cAccccAtG h GMCAUXT s.r

TCC

MC *ml

TCT

1215 0%

AhG

Lys 8.r

1305

-110

Ghc

hGh

WA

G’I-XTCCGCT

GM

MC

A,,

AGGGAGGCAT

15 TGT

GM

1245 CCA Pro

-130 ChGccAGMjc

CTI

MC

Am hr8

AGCACCGTGA

*IT

TAC

Tyr Lys Cl"

-140 GhGGhGhh~

CA&

CAG

Cy. Cl"

-150 CTGTAACTCT Thmh-

*TG

‘,-IA LmJ

TGT

2.740 2.800

3.040

2.580

2.530 CCACCGTGAA 2.590 IThhIGhGhC 2,650 chThmGGhT

hG2.6M 2.700

2.710 AAGATITIW

2.760

2.66G 2,720 *lThhhAmA

2.770

2.780

2.830 *crcTcGhGh

2,940 ATnrrrcAT

2.000

2.990 hhhThxh6I

2.900

2.930 ThhChChGch

2,940 Ahl-TcGhrTc

2.950 uTcchThM

ThCUhGhTI

2,990

3.000 AACTACATI-I

3.010 ACTcrcAcM

3.020 hTCCchhrIh

2.820

3.050

A-

3.070

2,960

3.080

GTAATGTTTI

CK2 1095 1110 1125 CTG CTC hhT GTG T I T GTC TGG A T T GGT T A T CTC TCC TCh GCT GTC AAT cch CTG Leu As” “al Phe "al Trp Ile Gly Tyr Leu Ser Ser *,a "al AS,, PT., bu

3.100

3.120 GhGChCh,Th

Le”

1155 1140 1170 1185 GTA T A T ACG TTC TTC AhT hhh ACT T A T AGG TCC CCC TTC TCA ACG T*C A T T CAC Val Tyr Thr Leu Phe Asn Lys Thr Tyr Ar6 Ser Ala Phe Ser *rg Tyr ,,e Cln N PKC

3.170

3.176 AATACAAA

FIG. 1. The cDNA sequence and deduced amino acid sequence of the rat 5-HT, serotonin receptor. The numbering refers to the DNA sequence. Positive numbers start at the first base of the initiation codon, and the 5’untranslated region is numbered negatively. The leucine zipper-like region is underlined with the leucine residues marked below the sequence by diamonds. Putative sites for post-translational modifications are marked with corresponding symbols below the sequence: N,N-linked glycosylation (Refs. (1, 18)); PKC, protein kinase C (Ref. (31)); and CK2, casein kinase II (Refs. (15, 17)).

SHORT

233

COMMUNICATION

function by being internalized into the cell, this putative leucine zipper is unlikely to be associated with regulatory functions of transcription factors. It may, however, play a role in other, yet unidentified types of intermolecular interaction. One possibility is the interaction with other membrane-associated proteins, either as a form of homodimers or in association with different factors/proteins to form heterologous complexes. To map the gene for the 5-HT, receptor, we analyzed the progeny of intersubspecific backcrosses (Kozak et aZ., 1990) in which females of the laboratory strains NFS/N, C58/J, or AKR/J were mated with Mus m. musculu..s (Skive) males and the F, females mated with mu.wu1u.s males. Genomic DNAs from parental and backcross mice were digested with restriction enzymes, size-fractionated on agarose gels, and transferred to nylon membranes as described before (Hoggan et al., 1988). A 5.1-kb cDNA clone, which contains the entire coding region for the rat 5-HT, receptor and some 5’ and 3’ untranslated regions, was used as the probe for Southern blot hybridization. The rat 5HT, receptor cDNA is expected to share a high degree of sequence homology with its mouse cognate since the mouse and rat 5-HT,c receptors share a 97% sequence homology (Yu et aZ., 1991). A clear restriction length variant was seen in Southern blot hybridization, as shown in Fig. 2. DNAs from all three inbred mouse parental strains produced the

11.8-kb PstI fragment that was absent from the musculus DNA sample. Forty-six of the 106 backcross progeny contained this fragment, consistent with single gene segregation. Comparison of the segregation pattern for this sequence with that of almost 200 markers typed in all 19 autosomes shows that the gene for the serotonin receptor, Htr-2, cosegregates with the Chr 14 marker Es-10 (Harris and Hopkinson, 1976). In fact, there were no recombinants detected between Htr-2 and Es-10 in the 106 backcross mice, indicating that the two loci are tightly linked (x” = 106, I’ < 0.0001). This region of Chr 14 contains a neuromuscular mutant, agitans (ug) (Hoecker et al., 1954). Homozygous agitans mice are characterized by arrested growth, tremor, and ataxia. These symptoms are associated with degeneration of Purkinje cells of the cerebellum and lesions in the spinal cord (Martinez and Sirlin, 1955). However, since little 5-HT, receptor mRNA is detected in cerebellum (Julius et rd., 1990), it appears unlikely that a defect in Htr-2 sequences could be responsible for this mutant phenotype. ACKNOWLEDGMENTS We thank Weiyin Li and M. Charlene Adamson for technical assistance. This work was supported by NIH Grant NS28190, a Biomedical Research grant from Indiana University School of Medicine, and a grant from Eli Lilly & Co. to L.Y.

REFERENCES abcde

f

9

-11.8

1.

BAUSE, E. (1963). Structural requirements of proteins. Eiochem. J. 209: 331-336.

2.

BRADLEY, P. B., ENGEL, G., FENIUK, W., FOZARD, J. R., HUMPNREY, P. P. A., MIDDLEMISS, D. N., MYLEZHARANE, E. J., RICHARDSON, B. P., AND SAXENA, P. R. (1966). Proposals for the classification and nomenclature of functional receptors for 5-hydroxytryptamine. Neuropharmncology 25: 563-576.

3.

BUSCH, S. J., AND SASSONE-CORSI, P. (1990). Dimers, leucine zippers and DNA-binding domains. Trends Genet. 6: 36-40. FARGIN, A., RAYMOND, J. R., LOHSE, M. J., KOBILKA, 8. K., CARON, M. G., AND LEFKOW~IX, R. J. (1966). The genomic clone G-21 which resembles a B-adrenergic receptor sequence encodes the 5-HT,* receptor. Nature 335: 356-360. FOZARD, J. R. (1989). “The peripheral actions of B-hydroxytryptamine,” pp. l-410, Oxford Univ. Press, Oxford. HARRIS, H., AND HOPKINSON, D. A. (1976). “Handbook of Enzyme Electrophoresis in Human Genetics,” North-Holland, Amsterdam. HARTIG, P. R. (1989). Molecular biology of 5-HT receptors. Trends Phnrmacol. Sci. 10: 64-69.

kb

4.

-

4.8 kb

5.

-

3.3 kb

6.

J

2.3 kb

7. 8.

HOECKER, G., MARTINEZ, (1954). Agitans, a new Hered. 45: 10-14.

9.

HOGGAN, M. D., HALDEN, N. F., BUCHLER, C. E., AND KOZAK, C. A. (1966). Genetic mapping of the mouse c-fms proto-oncogene to chromosome 18. J. Viral. 62: 1055-1056. HOYER, D. (1966). Functional correlates of serotonin 5-HT, recognition sites. J. Receptor Res. 8: 59-81.

7 2.1 kb FIG. 2. Southern blot analysis. Genomic DNAs from parental NFS/N (lane a) and backcross mice (lanes h-g) were digested with Pstl, blotted, and hybridized with a 5.1-kb cDNA probe for the 5HT, serotonin receptor.

of N-gIycosyIation

10.

A., MARKOVIC, S., AND PIZZARO, mutation in the house mouse.

0. J.

234

SHORT

COMMUNICATION

11. JULIUS, D., HUANG, K. N., LIVELLI, T. J., AXEL, R., AND JESSELL, T. M. (1990). The 5HT2 receptor defines a family of structurally distinct but functionally conserved serotonin receptors. Proc. Natl. Acad. Sci. USA 87: 928-932. 12. JULIUS, D., MACDERMOTT, A. B., AXEL, R., AND JESSELL, T. M. (1988). Molecular characterization of a functional cDNA encoding the serotonin lc receptor. Science 241: 558564. 13. KOBILKA, B. K., FRIELLE, T., COLLINS, S., YANG-FEN& T. L., KOBILKA, T. S., FRANCKE, Il., LEFKOWITZ, R. J., AND CARON, M. G. (1987). An intronless gene encoding a potential member of the family of receptors coupled to guanine nucleotide regulatory proteins. Nature 329: 75-79. 14. KOZAK, C. A., PEYSER, M., KRALL, M., MARIANO, T. M., KuMAR, C. S., PESTKA, S., AND MOCK, B. A. (1990). Molecular genetic markers spanning mouse chromosome 10. Genomics 8: 519-524. 15. KUENZEL, E. A., MULLIGAN, J. A., SOMMERCORN, J., AND KREBS, E. G. (1987). Substrate specificity determinants for casein kinase II as deduced from studies with synthetic peptides. J. Biol. Chem. 262: 9136-9140. 16. MBBERT, H., HOFFMAN, B. J., SNUTCH, T. P., VAN DYKE, T., LEVINE, A. J., HARTIC, P. R., LESTER, H. A., AND DAVIDSON, N. (1987). cDNA cloning of a serotonin 5-HTrc receptor by electrophysiological assays of mRNA-injected Xenopus oocytes.

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17. MARIN, O., MEGGIO, F., MARCHIORI, F., BORIN, G., AND PINNA, L. A. (1986). Site specificity of casein kinase-2 (TS) from rat liver cytosol: a study with model peptide substrates. Eur. J. Biochem. 160: 239-244. 18. MARSHALL, R. D. (1972). Glycoproteins. Annu. Rev. Biothem. 41: 673-702. 19. MARTINEZ, A., AND SIRLIN, J. L. (1955). Neurohistology of the agitans mouse. J. Comp. Neurol. 103: 131-137. 20. O’DOWD, B. F., LEFKOWITZ, R. J., AND CARON, M. G. (1989). Structure of the adrenergic and related receptors. Annu. Rev. Neurosci. 12: 67-83. 21. OVCHINNIKOV, Y. A. (1982). Rhodopsin and bacteriorhodop-

22. 23.

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