Studies on human kininogens. I. Isolation, characterization, and cleavage by plasma kallikrein of high molecular weight (HMW)-kininogen.

1. Human high molecular weight (HMW)-kininogen was highly purified from human plasma by chromatographies on QAE-Sephadex A-50 and CM-Sephadex C-50. Human HMW-kininogen thus purified was a mixture of a single chain and a disulfide-linked pair of chains. Human HMW-kininogen is an acidic glycoprotein having a molecular weight of 120,000. The amino acid composition of human HMW-kininogen is quite similar to that of bovine HMW-kininogen. 2. We investigated whether the liberation of kinin from human HMW-kininogen by human plasma kallikrein was accompanied by liberation of histidine-rich fragments, as observed with bovine HMW-kininogen (Han et al. (1975) J. Biochem. 77, 55--68). After prolonged incubation of human HMW-kininogen and human plasma kallikrein followed by gel-filtration on Sephadex G-50, a fragment of molecular weight 8,000 was isolated together with bradykinin. However, the histidine content of the fragment was not as high as that in the bovine fragments. Most of the histidine in human HMW-kininogen was recovered in the kinin-free protein, and the light chain of kinin-free protein was found to be rich in histidine compared with the heavy chain. These results suggest that the histidine-rich sequence in human HMW-kininogen is not released by the action of human plasma kallikrein, but remains bound to the light chain of kinin-free protein.     

Protein-protein interactions in contact activation of blood coagulation. Binding of high molecular weight kininogen and the 5-(iodoacetamido) fluorescein-labeled kininogen light chain to prekallikrein, kallikrein, and the separated kallikrein heavy and light chains

Binding of the 5-(iodoacetamido)fluorescein (IAF)-labeled high molecular weight (HMW) kininogen light chain to prekallikrein and D-Phe-Phe-Arg-CH2Cl-inactivated kallikrein was monitored by a 0.040 +/- 0.002 increase in fluorescence anisotropy. Indistinguishable average dissociation constants and stoichiometries of 14 +/- 3 nM and 1.1 +/- 0.1 mol of prekallikrein/mol of IAF-light chain and 17 +/- 3 nM and 0.9 +/- 0.1 mol of kallikrein/mol of IAF-light chain were determined for these interactions at pH 7.4, mu 0.14 and 22 degrees C. Prekallikrein which had been reduced and alkylated in 6 M guanidine HCl lost the ability to increase the fluorescence anisotropy of the IAF-kininogen light chain, suggesting that the native tertiary structure was required for tight binding. The kallikrein heavy and light chains were separated on the basis of the affinity of the heavy chain for HMW-kininogen-Sepharose, after mild reduction and alkylation of kallikrein under nondenaturing conditions. Under these conditions, alkylation with iodo [14C]acetamide demonstrated that only limited chemical modification had occurred. Binding of the IAF-kininogen light chain to the isolated alkylated kallikrein heavy chain, when compared to prekallikrein and kallikrein, was characterized by an indistinguishable increase in fluorescence anisotropy, average dissociation constant of 14 +/- 3 nM, and stoichiometry of 1.2 +/- 0.1 mol of kallikrein heavy chain/mol of IAF-light chain. In contrast, no binding of the D-Phe-Phe-Arg-CH2Cl-inactivated kallikrein light chain was detected at concentrations up to 500 nM. Furthermore, 300 nM kallikrein light chain did not affect IAF-kininogen light chain binding to prekallikrein, kallikrein, or the kallikrein heavy chain. The binding of monomeric single chain HMW-kininogen to prekallikrein, kallikrein, and the kallikrein heavy and light chains was studied using the IAF-kininogen light chain as a probe. Analysis of the competitive binding of HMW-kininogen gave average dissociation constants and stoichiometries of 12 +/- 2 nM and 1.2 +/- 0.1 mol of prekallikrein/mol of HMW-kininogen, 15 +/- 2 nM and 1.3 +/- 0.1 mol of kallikrein/mol of HMW-kininogen, 14 +/- 3 nM and 1.4 +/- 0.2 mol of kallikrein heavy chain/mol of HMW-kininogen, and no detectable effect of 300 nM kallikrein light chain on these interactions. We conclude that a specific, nonenzymatic interaction between sites located exclusively on the light chain of HMW-kininogen and the heavy chain of kallikrein or prekallikrein is responsible for the formation of 1:1 noncovalent complexes between these proteins.     

Two-generation reproduction study of di-2-ethylhexyl terephthalate in Crl:CD rats

BACKGROUND: This study was conducted to evaluate the potential adverse effects of di-2-ethylhexyl terephthalate (DEHT) on reproductive capability from exposure of F(0) and F(1) parental animals. METHODS: Four groups of male and female Crl:CD (SD)IGS BR rats (30/gender/group) were exposed to 0, 0.3%, 0.6%, and 1.0% DEHT in the feed for at least 70 consecutive days before mating for the F(0) and F(1) generations. Exposure for the F(0) and F(1) males continued throughout the mating period until euthanasia. Exposure for the F(0) and F(1) females continued throughout mating, gestation, and lactation. The F(1) and F(2) pups were weaned on postnatal day (PND) 21. Assessments included gonadal function, estrous cyclicity, mating behavior, conception rate, gestation, parturition, lactation, and weaning in the F(0) and F(1) generations, and F(1) generation offspring growth and development. RESULTS: DEHT exposure did not affect clinical observations. However, lethality was observed in F(0) and F(1) dams consuming the 1.0% diet during the post-weaning period. No treatment-related mortality occurred in any of the male groups exposed to DEHT or in the female groups exposed to 0.3% or 0.6% DEHT. Male rats consuming the 1.0% diet in both parental generations gained weight more slowly than the controls. There were no indications of adverse effects on reproductive performance in either the F(0) or F(1) generation. Male and female mating and fertility indices, pre-coital intervals, spermatogenic endpoints, reproductive organ weights, lengths of estrous cycle and gestation, live litter size, developmental landmarks, and postnatal survival were similar in all exposure groups. Additionally, ovarian follicle counts for the F(1) females in the high-exposure group were similar to the control values. No adverse exposure-related macroscopic pathology was noted at any exposure level in the F(0) and F(1) generations. CONCLUSIONS: Increases in liver weights were found in the male and female animals exposed to 0.6% or 1.0% DEHT in the diet. Because there were no accompanying histopathologic changes, this effect was not considered adverse. Significant decreases in feed consumption in the female animals from the groups consuming 1.0% DEHT in the diet during lactation accompanied reduced postnatal pup body weights and rate of weight gain. Reductions in pup body weights later in lactation may also have been due to direct consumption of the treated feed by the pups or taste aversion to the same. Reduced relative spleen weight was found in male weanling pups from the 1.0% group in both generations and reduced relative spleen and thymus weights were found in female pups from the 1.0% group in the F(2) generation at necropsy on PND 21. Therefore, for parental and pup systemic toxicity, 0.3% DEHT in the diet (182 mg/kg/day) was considered no-observed-effect level (NOEL). The 1.0% DEHT (614 mg/kg/day) in the diet exposure concentration was considered a NOEL for F(0) and F(1) reproductive toxicity endpoints.     

Hageman factor-dependent pathways: mechanism of initiation and bradykinin formation

The concentration of bradykinin in human plasma depends on its relative rates of formation and destruction. Bradykinin is destroyed by two enzymes: a plasma carboxypeptidase (anaphylatoxin inactivator) removes the COOH-terminal arginine to yield an inactive octapeptide, and a dipeptidase (identical to the angiotensin-converting enzyme) removes the COOH-terminal Phe-Arg to yield a fragment of seven amino acids that is further fragmented to an end product of five amino acids. Formation of bradykinin is initiated on binding of Hageman factor (HF) to certain negatively charged surfaces on which it autoactivates by an autodigestion mechanism. Initiation appears to depend on a trace of intrinsic activity present in HF that is at most 1/4000 that of activated HF (HFa); alternatively traces of circulating HFa could subserve the same function. HFa then converts coagulation factor XI to activated factor XI (XIa) and prekallikrein to kallikrein. Kallikrein then digests high-molecular-weight kininogen (HMW-kininogen) to form bradykinin. Prekallikrein and factor XI circulate bound to HMW-kininogen and surface binding of these complexes is mediated via this kininogen. In the absence of HMW-kininogen, activation of prekallikrein and factor XI is much diminished; thus HMW-kininogen has a cofactor function in kinin formation and coagulation. Once a trace of kallikrein is generated, a positive feedback reaction occurs in which kallikrein rapidly activates HF. This is much faster than the HF autoactivation rate; thus most HFa is formed by a kallikrein-dependent mechanism. HMW-kininogen is also therefore a cofactor for HF activation, but its effect on HF activation is indirect because it occurs via kallikrein formation. HFa can be further digested by kallikrein to form an active fragment (HFf), which is not surface bound and acts in the fluid phase. The activity of HFf on factor XI is minimal, but it is a potent prekallikrein activator and can therefore perpetuate fluid phase bradykinin formation until it is inactivated by the C1 inhibitor. In the absence of C1 inhibitor (hereditary angioedema) HFf may also interact with C1 and activate it enzymatically. The resultant augmented bradykinin formation and complement activation may account for the pathogenesis of the swelling characteristic of hereditary angioedema and the serologic changes observed during acute attacks.     

Age-related incidence of spontaneous tumors in SPF C57BL/6 and BDF1 mice]

Incidence of spontaneous tumors in C57BL/6 NCrj (CR), C5BL/6 CrSlc (SL) and B 6 Crj x DBA/2 NCrj F1 (BD) mice, which were reared under a barrier system and died natural death, were examined. Cohorts of mice in 200 to 300 each were purchased at 4 weeks of age and raised under SPF conditions. A large portion of the mice were used for various experiments between 3 and 30 months old while not a small number died before use and were autopsied. Median survival periods of the female and male were estimated at 697 and 680 days for CR, 764 and 806 days for SL and 866 and 929 days for BD, respectively. Incidence of spontaneous neoplastic lesions in the autopsied animals were 77.4% and 79.2% of 535 female and 590 male CR, 69.7% and 55.1% of 502 female and 463 male SL, and 75.8% and 78.0% of 298 female and 346 male BD, respectively. In CR, histiocytic sarcoma was the most predominant tumor, accounting for 72.1% of all tumors. In SL, malignant lymphoma was the most prevailing, forming 62.3%, and, in male BD, hepatocellular carcinoma was the most frequent, accounting for 41.8% of all tumors.     

Aspects related to productivity for four generations of a Lutzomyia longipalpis laboratory colony

A closed colony of Lutzomyia longipalpis was established with specimens collected in the Raposa - Serra do Sol indian reservoir, one of the main foci of visceral leishmaniasis in the State of Roraima, Brazil. Biological observations were made on four generations of a L. longipalpis colony with emphasis on productivity. Aspects studied were the number of laid and retained eggs, and the number of adults (male and female) per generation. During the four generations the percentage of engorged females that laid eggs varied from 64.2% (third generation-F3) to 90.3% (second generation-F2). The mean number of eggs laid per female varied from 23.6 (F3) to 39. 9 (first generation-F1). The maximum number of eggs laid per female varied from 84 (F3) to 124 (F1). The mean number of retained eggs per female was 12.7 (parental generation-P and F1) to 22.1 (F2). The number of females exceeded the number of males in all generations. However, significant difference for male/female ratio was found only for F3. Fecundity rates were between 42.1 (F3) and 58.3 (F2). From a total of 439 blood-fed females, 355 females laid 12,257 eggs that yield 5,354 adults (2,525 males and 2,829 females) in four generations. F2 presented maximum productivity and fecundity rates.     

Inheritance of resistance to promotion of preneoplastic liver lesions in Copenhagen rats

Previously, we have shown that Copenhagen (Cop) rats are highly resistant to the induction of putative preneoplastic, glutathione S-transferase 7-7- (GST 7-7) positive liver lesions following treatment with a modified resistant hepatocyte (RH) protocol. The objective of this study was to determine if resistance is inherited in a dominant or recessive manner and to derive an estimate of the number of genetic loci involved. We crossed male and female Cop rats with F344 rats to produce F1 offspring. Backcross rats were generated using female F1 rats and either Cop or F344 males, resulting in B1c and B1f generations, respectively. The male rats from all these crosses were initiated with diethylnitrosamine (200 mg/kg) at 7 to 8 weeks of age and were promoted 3 weeks later with the RH protocol (2-acetylaminofluorene and a two-thirds partial hepatectomy). The rats were sacrificed 3 weeks after the partial hepatectomy and their livers were sectioned and stained for GST 7-7-positive lesions. The susceptibility of F1 rats was in between Cop and F344 rats, having 21.7% +/- 2.0% (mean +/- SEM) of their liver volume occupied by lesions versus 4.2% +/- 0.8% for Cop and 53.0% +/- 5.8% for F344 rats. As expected, B1c rats had a volume of liver occupied by lesions that was in between the F1 and Cop rats at 13.5% +/- 1.6%. Surprisingly, B1f rats were similar to B1c rats in their resistance (9.1% +/- 2.1%). These results point to a complex, polygenic inheritance pattern that can be explained by a minimum of four loci, one of which shows recessive epistasis.     

烟草白粉病抗性基因的遗传分析

以烟草抗白粉病品种台烟7号为母本,感病品种NC89为父本,构建6个世代的群体,利用主基因 多基因混合遗传模型的分离分析方法,研究烟草白粉病的抗性遗传规律。结果表明,烟草白粉病抗性的遗传是由两对加性-显性-上位性主基因 加性-显性-上位性多基因（E-0模型）控制的。B1、B2和F2世代主基因的遗传率分别为88.05%、32.62%、84.43%,主基因遗传率很大,说明可以在抗病育种早期进行选择;B1、F2世代多基因遗传率均为0.00%,说明烟草白粉病的发生受一定环境影响。     

The inheritance of thiabendazole resistance in Haemonchus contortus.

Haemonchus contortus worm populations isolated from naturally infected sheep at the Pastoral Research Laboratory, Armidale, N.S.W., were found to contain approximately 20% of worms resistant to a 50 mg/kg dose of thiabendazole. Following 3 generations of selection with 50 mg/kg thiabendazole the number of worms removed by the anthelmintic was too small to detect differences between treated and control groups. After more than 15 generations of selection, matings between males from the selected strain and non-resistant females produced resistant males and females in equal numbers. Thus, thiabendazole resistance does not appear to be sex-linked. A dose--response assay on the F2 adults indicated that worms from female resistant x male non-resistant crosses were more resistant than F2 adults of the reciprocal cross. An in vitro technique that identified thiabendazole-resistant eggs by their ability to hatch in a solution containing thiabendazole and 0.1% NaCl solution was also used to study the inheritance of resistance. F1 eggs had similar LC50's to the resistant parents. F2 and back-cross eggs from an original mating of thiabendazole-resistant females x non-resistant males had a higher LC50 than F2 and back-cross eggs from the reciprocal mating, indicating a degree of matroclinous inheritance of resistance. However, the resistant parents had tolerances to thiabendazole exceeding those of F2. F3 eggs had a resistance distribution that ranged from that of the resistant to the non-resistant parent. No significant deviation from linearity was observed in any of the dose--response lines. These results indicate that thiabendazole resistance in H. contortus worms is inherited as an autosomal and semi-dominant trait.     

Inheritance of diflubenzuron resistance and monooxygenase activities in a laboratory-selected strain of Lucilia cuprina (Diptera: Calliphoridae).

Inheritance of the high-level diflubenzuron resistance shown by a laboratory-selected strain of Lucilia cuprina (Wiedemann) was examined in matings with a susceptible reference strain. Progeny of reciprocal crosses between resistant females and susceptible males showed higher LC50 values than the alternate reciprocal cross, indicating some maternal influence on inheritance of resistance. Resistance was inherited in a codominant (S male x R female) or incompletely recessive (R male x S female) manner. Monooxygenase activities (aldrin epoxidation) of the F1 generations were also intermediate between the levels shown by the parental lines, however, inheritance of enzyme activities showed greater degrees of dominance than for resistance levels. There was also some maternal influence on inheritance of monooxygenase activities. Backcrosses of F1 generations to both susceptible and resistant parents did not fit the expected patterns for a major sex-linked resistance locus, indicating that the maternal influence on resistance inheritance was not associated with sex-linkage of a major resistance gene. The backcross data also failed to fit the model for a single major autosomal gene, suggesting that the resistance in the diflubenzuron-selected strain is polygenic, involving mechanisms additional to monooxygenases.     

小麦雌性育性的主基因+多基因混合遗传分析

选用普通小麦中3种不同生态型育性正常品种与雌性不育系XND126杂交构建3个F2组合, 连续两年对3组合P₁、P₂、F₁和F₂雌性育性进行调查, 利用植物数量性状主基因+多基因混合遗传模型的4世代联合分析方法分析了小麦雌性育性的遗传。结果表明: 小麦雌性育性受两对主效基因+多基因联合控制, 两对主效基因之间存在互作效应。     

Evidence for maternal inheritance of mitochondrial DNA in allotetraploid.

The complete mitochondrial DNA (mtDNA) sequences of the allotetraploid and red crucian carp were determined in this paper. We compared the complete mtDNA sequences between the allotetraploid and its female parent red crucian carp, and between the allotetraploid and its male parent common carp. The results indicated that the complete mtDNA nucleotide identity (99.7%) between the allotetraploid and its female parent red crucian carp was higher than that (89.0%) between the allotetraploid and its male parent common carp. Moreover, the analysis on the start and stop codons, overlaps and spacers, and phylogeny of the mt genomes indicated the genetic relationship between the allotetraploid and its female parent red crucian carp was closer than that between the allotetraploid and its male parent common carp. Our results indicated that the allotetraploid mt genome was strictly maternally inherited. Through maternal inheritance, the mt genome in the F(11) allotetraploid displayed extremely high similarity to that in the female parent red crucian carp after 11 generations (from F(1) to F(11) hybrids). Such results indicated that the F(11) allotetraploid possessed the stable inheritance characteristic. Thus the tetraploid stocks possessed the good base to form a new tetraploid species in the future. Since the establishment of the new tetraploid stocks has the great significance in analyzing evolutionary theory of vertebrate and in improving aquaculture industry, analysis of the mt genome and the elucidation of the variation of the mt genome in the allotetraploid and its parents proved that it was a useful genetic marker to monitor the variations in the progeny of the crosses.     

Effect of a partial deletion of Y chromosome on in vitro fertilizing ability of mouse spermatozoa.

The effect of a partial deletion of Y chromosome on sperm fertilizing ability was investigated through an in vitro fertilization technique. Epididymal spermatozoa of a congenic line, B10.BR-Ydel, which is characterized by a high incidence of abnormal spermatozoa, revealed a significantly lower in vitro fertilization rate (22%) than that (79%) of its control strain (B10.BR/SgSn), which has a normal-sized Y chromosome. Incidence of capacitated spermatozoa as determined by chlortetracycline fluorescence assay was significantly lower in B10.BR-Ydel than in B10.BR/SgSn spermatozoa. The fertilization rate was significantly improved when B10.BR-Ydel spermatozoa were separated from the supernatant of sperm suspension by Percoll gradient centrifugation. A reconstitution experiment revealed that the B10.BR-Ydel spermatozoa were more sensitive to the inhibitory effect of the supernatant than B10.BR/SgSn spermatozoa. Spermatozoa from F1 (C57BL/6N male x B10.BR-Ydel female) males showed higher fertilization rates than those from F1 (B10.BR.Ydel male x C57BL/6N female) males. These observations suggest that not only the morphology but also the fertilizing ability of spermatozoa is directly related to partial deletion of Y chromosome.     

Production of offspring from cloned transgenic RFP female dogs and stable generational transmission of the RFP gene

The purpose of this study was to analyze the reproductive ability of transgenic female dogs born bysomatic cell nuclear transfer and to determine inheritance of the red fluorescent protein (RFP) transgene. The four founder transgenic bitches (F0) reached puberty at 340.8 ± 39.6 days after birth and were bred with wild-type male dogs by natural mating or by artificial insemination. The bitches all became pregnant and successfully delivered 13 puppies (F1), of which two females were bred with wild-type dogs to deliver 7 offspring (F2), including 1 stillbirth. Among the 19 live offspring, 10 puppies showed emission of RFP under UV light and the presence of the RFP transgene was confirmed by genomic PCR and Southern blot analyses. In conclusion, transgenic RFP female dogs exhibited normal reproductive ability and expression of the transgene was demonstrated in F1 and F2 generations.     

鲜食番茄果实中番茄红素含量的主基因－多基因混合遗传分析

选择2个番茄红素含量显著不同的鲜食番茄品系,通过P₁、P₂、F₁、F₂、B₁和B₂6世代联合分析法,研究分析了番茄红素的遗传规律。结果表明：番茄红素的遗传符合一个主基因和加性－显性－上位性多基因模型,主基因遗传力在B₁、B₂和F₂分别为6.85%、34.78％和58.33％,多基因遗传力在B₁、B₂和F₂分别为58.48％、30.69％和0。      

Characterization of the H-kininogen-binding site on factor XI: a comparison of factor XI and plasma prekallikrein.

Factor XI (FXI), the zymogen of the blood coagulation protease FXIa, and the structurally homologous protein plasma prekallikrein circulate in plasma in noncovalent complexes with H-kininogen (HK). HK binds to the heavy chains of FXI and of prekallikrein. Each chain contains four apple domains (F1-F4 for FXI and P1-P4 for prekallikrein). Previous studies indicated that the HK-binding site on FXI is located in F1, whereas the major HK-binding site on prekallikrein is in P2. To determine the contribution of each FXI apple domain to HK-FXI complex formation, we examined binding of recombinant single apple domain-tissue plasminogen activator fusion proteins to HK. The order of affinity from highest to lowest is F2 F4 > F1 F3. Monoclonal antibodies against F2 are superior to F4 or F1 antibodies as inhibitors of HK binding to FXI. Antibody alphaP2, raised against prekallikrein, cross-reacts with FXI F2 and inhibits FXI-HK binding with an IC(50) of 8 nm. HK binding to a platelet-specific FXI variant lacking the N-terminal half of F2 is reduced > 5-fold compared with full-length FXI. A chimeric FXI molecule in which F2 is replaced by P2 is cleaved within P2 during activation by factor XIIa, resulting in greatly reduced HK binding capacity. In contrast, wild-type FXI is not cleaved within F2, and its binding capacity for HK is unaffected by factor XIIa. Our data show that HK binding to FXI involves multiple apple domains, with F2 being most important. The findings demonstrate a similarity in mechanism for FXI and prekallikrein binding to HK.     

白菜叶裂数性状主基因+多基因遗传分析

以叶片全缘的大白菜自交系(P1)和叶缘深裂的欧洲白菜型油菜自交系(P2)杂交所获得的6个基本世代(P1、P2、F1、B1、B2、F2)为材料,应用主基因+多基因混合遗传模型对白菜叶裂数进行遗传分析。结果表明,白菜的叶裂数受2对加性-显性-上位性主基因+加性-显性多基因的控制,第1对主基因加性效应为-1.154 7,显性效应为-1.516 8;第2对主基因的加性效应为-1.154 8,显性效应为1.034 9;多基因加性效应为0.591 9,显性效应为1.145 2,2对主基因间存在明显的交互作用。B1、B2和F2世代叶裂数的主基因遗传率分别为88.48%、90.40%、93.03%;多基因遗传率分别为4.114%、0、0。B1、B2、F2世代叶裂数表现出较高的主基因遗传率,受环境影响较小。在白菜叶裂数性状的改良中应以主基因为主,并适于早代选择。     

Parental effects in the inheritance of nonnodulation in peanut

A nonnodulating line (M4-2) and three normal nodulating lines (UF 487A, PI 262090, and Florunner) of peanut (Arachis hypogaea L.) were crossed in full diallel to investigate the inheritance of nodulation. Data from F1, F2, F3, F1BC1, and F2BC1 generations indicated that three genes control nodulation at three independent loci, with nodulation being a product of two genes and inhibited by a third gene when it is dominant and the others are homozygous recessive. A genetic model has been proposed that describes the nonnodulated genotypes as n1n1n2n2N3N3 or n1n1n2n2N3n3 and all other genotypes as normally nodulated except n1n1N2n2N3-, which has reduced nodulation when the n1n2N3 male gamete unites with the n1N2- female gamete or when the n1n2n3 male gamete unites with the n1N2N3 female gamete.     

Steroid-independent male sexual behavior in B6D2F2 male mice

It is well established that male sexual behavior (MSB) is regulated by gonadal steroids; however, individual differences in MSB, independent of gonadal steroids, are prevalent across a wide range of species, and further investigation is necessary to advance our understanding of steroid-independent MSB. Studies utilizing B6D2F1 hybrid male mice in which a significant proportion retain MSB after long-term orchidectomy, identified as steroid-independent-maters (SI-maters), have begun to unravel the genetic underpinnings of steroid-independent MSB. A recent study demonstrated that steroid-independent MSB is a heritable behavioral phenotype that is mainly passed down from B6D2F1 hybrid SI-maters when crossed with C57BL6J female mice. To begin to uncover whether the strain of the dam plays a role in the inheritance of steroid-independent MSB, B6D2F1 hybrid females were crossed with B6D2F1 hybrid males. While the present study confirms the finding that steroid-independent MSB is a heritable behavioral phenotype and that SI-mater sires are more likely to pass down some components of MSB than SI-non-maters to their offspring, it also reveals that the B6D2F2 male offspring that were identified as SI-maters that displayed the full repertoire of steroid-independent MSB had the same probability of being sired from either a B6D2F1 SI-mater or SI-non-mater. These results, in conjunction with previous findings, indicate that the specific chromosomal loci pattern that codes for steroid-independent MSB in the B6D2F2 male offspring may result regardless of whether the father was a SI-mater or SI-non-mater, and that the maternal strain may be an important factor in the inheritance of steroid-independent MSB.     

Inheritance of steroid-independent male sexual behavior in male offspring of B6D2F1 mice

The importance of gonadal steroids in modulating male sexual behavior is well established. Individual differences in male sexual behavior, independent of gonadal steroids, are prevalent across a wide range of species, including man. However, the genetic mechanisms underlying steroid-independent male sexual behavior are poorly understood. A high proportion of B6D2F1 hybrid male mice demonstrates steroid-independent male sexual behavior (identified as “maters”), providing a mouse model that opens up avenues of investigation into the mechanisms regulating male sexual behavior in the absence of gonadal hormones. Recent studies have revealed several proteins that play a significant factor in regulating steroid-independent male sexual behavior in B6D2F1 male mice, including amyloid precursor protein (APP), tau, and synaptophysin. The specific goals of our study were to determine whether steroid-independent male sexual behavior was a heritable trait by determining if it was dependent upon the behavioral phenotype of the B6D2F1 sire, and whether the differential expression of APP, tau, and synaptophysin in the medial preoptic area found in the B6D2F1 sires that did and did not mate after gonadectomy was similar to those found in their male offspring. After adult B6D2F1 male mice were bred with C57BL/6J female mice, they and their male offspring (BXB₁) were orchidectomized and identified as either maters or “non-maters”. A significant proportion of the BXB₁ maters was sired only from B6D2F1 maters, indicating that the steroid-independent male sexual behavior behavioral phenotype of the B6D2F1 hybrid males, when crossed with C57BL/6J female mice, is inherited by their male offspring. Additionally, APP, tau, and synaptophysin were elevated in in the medial preoptic area in both the B6D2F1 and BXB₁ maters relative to the B6D2F1 and BXB₁ non-maters, respectively, suggesting a potential genetic mechanism for the inheritance of steroid-independent male sexual behavior.