Exclusion of Sall 4 as the sex-determining gene in the Mandarin vole Microtus mandarinus mandarinus.

In previous studies, we have shown that the Sry HMG-box is absent in Microtus mandarinus mandarinus (M. m. mandarinus), suggesting that sex determination of M. m. mandarinus is independent of the Sry gene. We amplified a 312 bp fragment within exon 2 of the Sall4 gene in the mouse and M. m. mandarinus using polymerase chain reaction (PCR) and detected Sall4 using fluorescence in situ hybridization (FISH) technique. The probes for the Sall4 gene were labeled with digoxigenin using PCR and hybridized to chromosomes and interphase nuclei of the mouse and M. m. mandarinus. Our results suggested that Sall4 exists in the genome of male and female M. m. mandarinus, and the sequence within exon 2 of the gene is the same in the mouse and M. m. mandarinus. The results also showed that Sall4 is localized on chromosome 6 in M. m. mandarinus. As they are the sex chromosomes in M. m. mandarinus, the results excluded the Sall4 gene from being the testis-determining factor in this species. We propose that in M. m. mandarinus, sex determination is controlled by another yet unknown gene on the sex chromosomes.

Two new karyotypes and bandings in Microtus mandarinus faeceus (Rodentia).

Here we report our study on two new karyotypes and C-bandings of M. m. faeceus. Our study shows that there are polymorphisms in the X chromosome of M. m. faeceus (Rodentia), which exibitsubtelocentric X(ST), metacentric X(M) and submetacentric X(SM) patterns, respectively. One new karyotype formula is: 2n = 49 = 4sm + 42t + 1m + XX (sm,sm), and the sex chromosomes are: X(M) X(SM); The other new karyotype formula is: 2n = 50 = 4sm + 43t + 1m + XX (sm,sm), and the sex chromosomes are: X(SM)X(SM). One C-banding karyotype formula is: 2n = 49 = 4sm + 44t + X(st)0, and the sex chromosome is: X(ST)O and the other C-banding karyotype formula is: 2n = 50 = 4sm + 44t + XY(m,t), and the sex chromosomes are: X(M) Y.

[Recent advances on sex determining mechanisms of Microtus mandarinus].

Most mammalian sex determination belongs to male heterogametic type of genetic sex determination. Sex determination of most mammals depends on the Y chromosome. SRY gene is the testis-determining factor on Y chromosome of most mammals, which is thought to be the most important gene in sex determination by far. Recent studies on Microtus mandarinus mandarinus demonstrated that the subspecies has Y chromosome, but there is no SRY gene on Y chromosome. Sex determination of Microtus mandarinus mandarinus is independent of SRY gene. R-spondin1 has also been excluded as the sex determination gene of Microtus mandarinus mandarinus. This paper reviews recent advances on sex determining mechanisms of Microtus mandarinus mandarinus. Possible sex determining mechanisms of Microtus mandarinus mandarinus in the absence of SRY gene are also discussed.

[An overview of phylogenetic relationship between Mus and Microtus].

Muriod is the most successful one among rodents struggling for existence, and biologists have been paying much attention to it, especially Mus musculus. Because of the thorough study on Mus musculus, it has been widely applied in lab, and becomes a good material for studying other animals. Phylogenetic relationship between different species and populations of Mus and Microtus are more clearly revealed with some genetic markers of modern genetics, such as protein, mtDNA, and rDNA. Taxonomy and evolution of species of both genus have also been revealed. Whereas the taxonomy and genetic relationships of some species and populations between both genus need to be further studied.

Sex determination of Microtus mandarinus mandarinus is independent of Sry gene.

PCR was performed with primers corresponding to the Sry HMG-box of the mouse and eight Microtus species. Primers for the SALL4 gene and the ZFY/ZFX gene were used as positive controls. None of these sets of primers can amplify any homologous segment of the Sry gene in the genomic DNA of Microtus mandarinus mandarinus, but both can amplify the Sry HMG-box in the male mouse, SALL4 bands, and ZFY/ZFX bands in both male and female M. m. mandarinus and mouse. Southern blotting was also used. We used primers for the mouse Sry HMG-box to amplify the Sry HMG-box of the mouse, Microtus arvalis (Microtus), and Pitymys duodecimcostatus (Microtus). The probes were labeled with digoxigenin using PCR after being sequenced. Southern blots were used to detect the genomic DNA of M. m. mandarinus using alkaline phosphatase detection. The results showed that there was a 3.95-kb-blotting band in positive controls: mouse, Microtus arvalis, and Pitymys duodecimcostatus. However, no homologous sequence of the Sry HMG-box was detected in the genomic DNA of M. m. mandarinus. Therefore, we speculate that the Sry HMG-box of M. m. mandarinus is absent or had a big change; sex determination of M. m. mandarinus is independent of Sry. The sex determination mechanism without Sry of M. m. mandarinus is also discussed.

[A study on the karyotype, C-banding and Ag-NORs in Rana nigromaculata].

The chromosome samples of Rana nigromaculata were prepared by peripheral blood lymphocyte cultured in vitro. Karyotype, C-banding and silver-staining nucleolus organizer regions (Ag-NORs) were observed on chromosomes samples. The result showed that: (1) the chromosome number of Rana nigromaculata is 26 (2n=26), i.e., 10 large and 16 small chromosomes, the large chromosomes are matched into 5 homologous pairs and small chromosomes are matched into 8 homologous pairs, and further indicates the karyotype of Rana nigromaculata is bi-modal; (2) Metaphases of female and male were observed separately, the chromosome of No.11 has a pronounced secondary constriction in the middle of long arms. But the position of secondary constriction in the aberrant type individuals is in the middle of long arms of the No.8; (3) it has only one obvious C-banding close to the telomere, which is located in the long arms of the No.5; (4) The chromosome No.11 is a pair of homologous chromosomes with Ag-NORs, and the position of Ag-NORs in female and male is identical.

Numerical and structural variations of the X chromosomes and no. 2 autosomes in mandarin vole, Microtus mandarinus (Rodentia).

Here we describe our studies on Microtus mandarinus faeceus of Jiangyan in Jiangsu province of China. By karyotype and G-banding analysis we have found variation in chromosome number and polymorphisms of the X chromosome and the second pair of autosomes of the subspecies. Chromosome number of the subspecies is 2n=47-50. The subspecies has three kinds of chromosomal sex: XX, XO and XY, among which one of the X chromosomes is subtelocentric (X(ST)) and the other is metacentric (X(M)). After comparing karyotypes of different subspecies, we found the specific cytogenetic characteristics of Microtus mandarinus, that is they have three kinds of chromosomal sex: XX, XO and XY; X chromosomes are heteromorphic; the chromosome number of female individuals are one less than male individuals; chromosome number of XX individuals are equal to that of XO ones. We hypothesize that Robertsonian translocation is the main reason of the polymorphism of the second pair of autosomes and variety of chromosome number, and it also causes the chromosome number evolution in different subspecies of Microtus mandarinus.

[The effect of CSN1 S2, CSN3 and beta-lg genes on milk performance in Xinong Saanen dairy goat].

PCR-RFLP technique was applied to analyze correlation between the polymorphisms of CSN1 S2 (alpha(s2) casein), CSN3 (kappa casein) and beta-lg (beta-lactoglobulin) genes and milk performance in 69 individuals of Xinong Saanen dairy goat. The results showed that there was significant correlation between different genotypes of CSN1 S2 locus and milk yield:average milk yield of individuals with genotype FF was less than that of genotype NN (P < 0.05); the second lactation milk yield of individuals with genotype NN was over 90 kg higher than that with genotype FF (P < 0.01). This indicates that allele F of CSN1 S2 locus probably has significant negative effect on milk yield. The results of CSN3 gene digested with endonuclease Hind III cleavage showed that no significant difference of milk yield between genotype DE and genotype EE was detected in first, second, third and fourth lactation milk yield and average milk yield (P > 0.05). The results of CSN3 gene with endonuclease Taq I cleavage showed that no significant difference of milk yield among individuals with genotype TT, TC and CC was detected (P > 0.05). No polymorphism was detected in PCR products of CSN3 gene digested with endonuclease Hae III. The analysis of beta-lg gene's 5' flanking region (710 bp) by PCR-RFLP in Xinong Saanen dairy goat showed that milk yield of individuals with genotype AA was higher than that with genotype AB in second, third lactation milk yield and average milk yield (P < 0.05). The results implied that allele A of beta-lg gene's 5' flanking region is probably related to high milk yield.

The origin of the genetical diversity of Microtus mandarinus chromosomes.

Here we describe our comparative studies on two types of X chromosomes, namely X(M) and X(SM,) of the mandarin vole (Microtus mandarinus). By chromosome G- and C-banding analysis, we have found that two different types of X chromosomes exist in mandarin voles. The two types of X chromosomes present two different G- and C-banding patterns: the X(M) chromosome is a longer metacentric X chromosome which is C-band negative; and the X(SM) is a shorter submetacentric X chromosome which has one C-band at the centromere and another one at the middle part of the short arm. The X(SM) has 6 G-bands including one on the kinetochore, one in the middle of the short arm, and four on the long arm. The X(M) has 7 G-bands including one on the kinetochore, two on the short arm, and four on the long arm. We have further found that female voles can be grouped into three types based on the composition of the X chromosome but the male voles have only one type. The three female groups are: (1) female voles (X(M)X(SM)), in which the two X chromosomes are different, the longer one is metacentric and the shorter is submetacentric; (2) female vole (X(SM)X(SM)), in which the two X chromosomes are both submetacentric; (3) female vole (X(M)O), in which there is only one X chromosome that is metacentric. Surprisingly, we have never found female voles with X(M)X(M), females with X(SM)O or males with X(M)Y. We hypothesize that the X(SM) chromosome is derived from the X(M) through its breakage and re-joining. The paper also discusses the formation of X(M)O females.

[Detection of Y chromosome in human and Microtus mandarinus with FISH].

The purpose of the investigation was to detect the Y chromosome of human and Microtus mandarinus with the satellite DNA probe in human's Yq by fluorescence in situ hybridization(FISH). We hybridizied the probe with the metaphase chromosome and interphase nucleus specimens of humanbeing and Microtus mandarinus respectively. The results showed that there was hybridization signal on metaphase chromosome and interphase nucleus of human, but no signal on metaphase chromosome and interphase nucleus of Microtus mandarinus. According to the results,we discussed the homologue between pY3.4 in Y chromosome of humanbeing and DNA of Microtus mandarinus and FISH result of Microtus mandarinus.

[A family history of vitiligo with autosomal dominant inheritance].

A family history of vitiligo was reported in this paper,and the reason causing disease was discussed. We think that the vitiligo in the family history is caused by autosomal dominant inheritance.