Analysis of human biologics with a mouse skin transplant model in humanized mice.

Preclinical testing of human therapeutic monoclonal antibodies has been limited in murine models due to species differences in pharmacokinetics and biologic responses. To overcome these constraints we developed a murine skin transplant model in humanized mice and used it to test human monoclonal antibody therapy. Neonatal NOD/SCID/IL2Rγc(null) mice (NSG) were reconstituted with human CD34(+) hematopoietic stem cells (hNSG). When adult, these mice rejected MHC mismatched murine C57BL/6J skin grafts. Rejection required adequate reconstitution with human cells. There was diffuse infiltration of the epidermis and dermis with hCD8 and hCD4 cells in rejected grafts by immunohistochemistry. Studies with B6/MHC class I and II knockout mice donors indicated that neither is required for rejection. Graft rejection was associated with the development of effector and central memory T cells and an increase in serum immunoglobulins. We also tested the effects of teplizumab (anti-CD3 mAb) and found it could delay skin graft rejection, whereas ipilimumab (anti-CTLA-4 [cytotoxic T-lymphocyte antigen-4] mAb) treatment accelerated rejection. These findings demonstrate that hNSG mice reliably and predictably reject a xenogenic mouse skin graft by a human T cell mediated mechanism. The model can be utilized to investigate the ability of human immunotherapies to enhance or suppress functional human immune responses.

Custom fluorescent-nucleotide synthesis as an alternative method for nucleic acid labeling.

The variety of potentially useful dyes or haptenes available for fluorescent nucleic acid hybridization assays is far greater than what can be obtained from commercial sources. Since this diversity could be useful in many laboratory applications, we have developed a simple and inexpensive procedure for preparing nonpurified labeled nucleotides, for use in common nucleic acid labeling reactions, such as PCR and nick translation. The modified nucleotides were synthesized by coupling allylamine-dUTP to the succinimidyl-ester derivatives of the fluorescent dyes or haptenes such as biotin or digoxigenin, which require fluorescently labeled proteins for detection. This method allows custom preparation of most common fluorescent nucleotides and rapid testing of new ones, while reducing the cost of procedures such as multiplex fluorescent in situ hybridization (M-FISH) by 100-200 fold.

Triple-color FISH analysis of 12p amplification in testicular germ-cell tumors using 12p band-specific painting probes.

Forty-nine surgical specimens and nine germ cell tumor lines were analyzed by triple-color FISH using microdissected probes for the cytogenetic bands of chromosome arm 12p (12p11.2, p12, and p13). FISH analysis demonstrated amplification of material from all three bands in all tumors. This amplification was in the form of increased copy number of 12p or i(12p) and/or 12p amplified regions (AMP12p). The number of copies of 12p was variable (4-11 copies) from case to case but tended to remain relatively constant in all clones of the same tumor, even when the amplification took the form of an amplified region composed of 12p material. In tumors with multiple clones, i(12p) and AMP12p were never found in the same cell. No correlation was found between 12p copy number and tumor type. We describe, for the first time, a relative overrepresentation of 12p13 or 12p12-p13 regions in six tumors (two surgical samples and four cell lines), either as "partial 12p" (five cases) or within a 12p amplified region (one case). The ubiquitous amplification of all three 12p bands in germ-cell tumors supports the hypothesis that 12p harbors more than one gene important for oncogenesis of adult male germ-cell tumors, and that these genes may be located in different areas of 12p.

Simple method for preparation of fluor/hapten-labeled dUTP.

Many projects, such as multiplex-fluorescence in situ hybridization (M-FISH) karyotyping, require the use of relatively large amounts of multiple fluor- or hapten-labeled nucleotides for the preparation of DNA probes. Such a requirement makes these experimental approaches prohibitively expensive for many researchers. The cost of such nucleotides can be reduced approximately 99% by purchasing the chemical precursors, fluor or hapten succinimidyl esters and 5-(3-aminoallyl)-2'-deoxyuridine 5' triphosphate (AA-dUTP), and performing the simple coupling/purification described here. It is possible to finish four to ten different fluor/hapten dUTP preparations of 2.5 microM scale within a 24 h period. The reagent cost for each preparation ranges from $33-$237 per microM, depending on the fluor/hapten. This laboratory uses such nucleotide preparations to prepare FISH probes by nick translation or PCR amplification.

Multiplex PCR: critical parameters and step-by-step protocol.

By simultaneously amplifying more than one locus in the same reaction, multiplex PCR is becoming a rapid and convenient screening assay in both the clinical and the research laboratory. While numerous papers and manuals discuss in detail conditions influencing the quality of PCR in general, relatively little has been published about the important experimental factors and the common difficulties frequently encountered with multiplex PCR. We have examined various conditions of the multiplex PCR, using a large number of primer pairs. Especially important for a successful multiplex PCR assay are the relative concentrations of the primers at the various loci, the concentration of the PCR buffer, the cycling temperatures and the balance between the magnesium chloride and deoxynucleotide concentrations. Based on our experience, we propose a protocol for developing a multiplex PCR assay and suggest ways to overcome commonly encountered problems.

Alteration in expression of the rat mitochondrial ATPase 6 gene during Pneumocystis carinii infection.

BACKGROUND: Pneumocystis carinii causes pneumonia in immunocompromised patients with a high morbidity and mortality rate, but the interaction between this organism and the host cell is not well understood. The purpose of this research was to study the response of host cells to P. carinii infection on a molecular level. RESULTS: The technique of mRNA differential display was used to detect genes whose expression may be affected by P. carinii infection. The nucleotide sequence of one differentially displayed DNA fragment was found to be identical to that of the rat mitochondrial ATPase 6 gene, which is a subunit of the F0F1-ATP synthase complex. A four-fold increase in expression of this gene was verified by Northern blot analysis of total RNA extracted from P. carinii-infected rat lung versus that from mock-infected rat lung. Localization of the cells containing ATPase 6 mRNA was accomplished by in situ hybridization. In sections of non-infected rat lung, these cells were found lining the distal parts of the respiratory tree and in apical areas of the alveoli. Histological location of these cells suggested that they were Clara cells and type II pneumocytes. This hypothesis was confirmed by co-localizing the mRNAs for ATPase 6 and surfactant protein B (SP-B) to the same cells by two-color fluorescent in situ hybridization. CONCLUSIONS: The ATPase 6 gene is over expressed during P. carinii infection, and type II pneumocytes and Clara cells are the cell types responsible for this over-expression.

Mild "duplication 6q syndrome": a case with partial trisomy (6)(q23.3q25.3).

We report on a female infant with partial 6q trisomy (46,XX,dir dup(6)(q23.3q25.3)) and phenotypic characteristics of the "duplication 6q syndrome," including intrauterine growth retardation, dolichocephaly, depressed nasal bridge, almond-shaped palpebral fissures, short neck, flexion-contractures of the wrists, and mild generalized hypertonia. Although clearly belonging to the described "duplication 6q syndrome," her features were milder than those found in the literature. Comparison of the phenotype of this child with other published reports indicates that specific phenotypic components of the duplication 6q syndrome cannot be attributed to duplication of a specific band or bands on 6q.

A case with mosaic di-, tetra-, and octacentric ring Y chromosomes.

A newborn female infant presented with abnormalities of the external genitalia including a 3 x 1 cm phallic structure, a perineal urethral opening, bifid scrotum, and a single urogenital opening. Peripheral blood karyotype was 45,X[81]/46,X,+r(Y)[19], however, there were no signs of Ullrich-Turner syndrome. High resolution G-banding as well as C- and Q-banding did not demonstrate any specific banding pattern or presence of heterochromatin on the ring. However, it was noticed that some of the rings were larger than others. FISH with a probe for Yq12 was negative in all metaphases studied. A Y-specific paint probe hybridized to the entire ring chromosome, confirming its origin. PCR analysis showed the presence of the SRY locus and of proximal Yq locus DYS271. Triple color FISH with probes for the Y centromere, DYZ5 (Yp), and all human telomeres showed the existence of different types of rings, some dicentric, some tetracentric, and some probably octacentric. Owing to the increased risk for gonadoblastoma, a surgical removal of the gonads was performed.

PCR and FISH analysis of a ring Y chromosome.

A newborn male infant presented with midshaft hypospadias, chordee, and undescended left testis. Both gonads lacked the tunica albuginea and appeared to be adjacent to structures resembling fallopian tubes. On biopsy, there was marked dysgenesis of both gonads, with a paucity of testicular tubules and foci of ovarian-like stroma. Peripheral blood karyotype was 46,X,mar(Y) [39]/45,X [5]. Right gonadal biopsy material showed the same mosaicism but with a higher proportion of 45,X cells (46%). PCR and FISH analyses with primers/probes from different Yp, Yq, and Ycen loci defined the structure of the marker Y as a probable complex ring with breakpoints in Yq11.21 (very close to the centromere) and in Yp11.32 (the pseudoautosomal region). Based on the phenotype and the laboratory findings, the prognosis given to the patient was for short stature and azoospermia without an increased risk for gonadoblastomas.

Molecular cytogenetic analysis of patients with holoprosencephaly and structural rearrangements of 7q.

The holoprosencephaly (HPE) sequence is a malformation complex with abnormal midline cleavage of the embryonic forebrain. HPE is genetically heterogeneous with at least 6 different chromosome regions containing genes involved in the expression of the phenotype. HPE3, recently identified as the human Sonic hedgehog gene, is localized to 7q36. We have used fluorescence in situ hybridization (FISH) and polymerase chain reaction (PCR) amplification in 5 cell lines from patients with HPE (3 cases), HPE and sacral agenesis (1 case), and microcephaly (1 case) to further define the structural rearrangements of the long arm of chromosome 7 in each case. All cell lines demonstrated loss of material in the critical region of HPE3 at band 7q36, which includes the Sonic hedgehog gene. We report here the analysis of these patient cell lines.

Characterization of multiple 12p rearrangements in testicular germ cell tumor cell line 833K and its subclone 64CP by chromosome microdissection.

Rearrangements of chromosome arm 12p are known to be common in germ cell tumors (GCT). Previous studies, using fluorescence in situ hybridization (FISH) with a whole chromosome 12 painting probe, showed unusual distributions of chromosome 12-derived chromatin in GCT cell line 833K and its cisplatin-resistant subclone, 64CP, located next to AgNOR (silver staining nucleolus organizer regions), some of which were ectopic. In this study, the ectopic stalk regions were shown by FISH to be composed of 18s and 28s rDNA, but were flanked by beta-satellite DNA, which may form a barrier around the rDNA. In order to determine the specific origins of the rearranged chromosome 12 segments, three different derived chromosome 12 regions were isolated from 64CP, using chromosomal microdissection. The microdissected fragments were labeled and hybridized by FISH to normal human chromosomes. All three segments localized to distal 12p; 12p12-->12pter, but with apparently different breakpoints for each segment. Furthermore, three-color FISH experiments with 12p band-specific probes demonstrated that the derivative chromosome 12 regions in 833K also originate from distal 12p (12p12-->p13). These sequences now can be evaluated for degree of overlap or common breakpoints which may be of significance in the development or progression of GCT.

Protein-tyrosine phosphatase Shp-2 regulates cell spreading, migration, and focal adhesion.

Shp-2, a widely expressed cytoplasmic tyrosine phosphatase with two SH2 domains, is believed to participate in signal relay downstream of growth factor receptors. We show here that this phosphatase also plays an important role in the control of cell spreading, migration, and cytoskeletal architecture. Fibroblast cells lacking a functional Shp-2 were impaired in their ability to spread and migrate on fibronectin compared with wild-type cells. Furthermore, Shp-2 mutant cells displayed an increased number of focal adhesions and condensed F-actin aggregation at the cell periphery, properties reminiscent of focal adhesion kinase (FAK)-deficient cells. This is consistent with our previous observations in vivo that mice homozygous for the Shp-2 mutation died at midgestation with similar phenotype to FAK and fibronectin-deficient embryos, having severe defects in mesodermal patterning, particularly the truncation of posterior structures. Biochemical analysis demonstrated that FAK dephosphorylation was significantly reduced in Shp-2 mutant cells in suspension. Furthermore, regulated association of Src SH2 domain with FAK and paxillin during cell attachment and detachment on fibronectin was disrupted in Shp-2 mutant cells. This report defines a unique role of the Shp-2 tyrosine phosphatase in cell motility, which might guide the design of a new strategy for pharmaceutical interference of tumor metastasis.

Chromosome instability contributes to loss of heterozygosity in mice lacking p53.

The p53 tumor suppressor protein participates in multiple cellular processes including cell cycle checkpoints and programmed cell death. In cell lines, loss of p53 function is associated with increased genetic instability including aneuploidy, gene amplification, and point mutation. Although similar genetic instability often accompanies the progression of malignancy in tumors, its role in tumor initiation in normal cells is not clear. To study whether or not loss of p53 leads to genetic instability in normal cells in vivo, we have examined mechanisms of loss of heterozygosity (LOH) at the Aprt (adenine phosphoribsyltransferase) and flanking loci in normal fibroblasts and T lymphocytes of p53-deficient mice. Somatic cell variants that arose in vivo as a consequence of genetic or epigenetic alterations abolishing Aprt function were selected and expanded in vitro by virtue of their resistance to 2,6-diaminopurine (DAP). We observed that p53 null mice produced about three times as many DAP-resistant fibroblast colonies than wild-type mice, but the frequency of DAP-resistant T lymphocyte colonies was not significantly changed. Mitotic recombination, but not point mutation, partly accounted for the increase in the frequency of DAP-resistant fibroblasts. Most significantly, chromosome loss/duplication and interstitial deletion, which were extremely rare events in the wild-type mice, represented a significant proportion of LOH events in both fibroblasts and T lymphocytes of p53 null mice. Also, increased interstitial deletion was observed in fibroblasts of p53 heterozygous mice. These data suggest that increased genetic variation, including chromosome instability, starts at the initiation stage of tumorigenesis when functional p53 is absent or reduced.

Rapid screening of the Y chromosome in idiopathic sterile men, diagnostic for deletions in AZF, a genetic Y factor expressed during spermatogenesis.

A rapid molecular screening programme has been established for the long arm of the human Y chromosome in Yq11 in order to quickly detect small interstitial deletions in this chromosome region. They have been observed in idiopathic sterile males with azoospermia and a severe oligozoospermia and are therefore indicative for deletion of AZF gene sequences. AZF (i.e. azoospermia factor) is a genetic factor located in Yq11 which controls human spermatogenesis. The screening programme is based mainly on a multiplex PCR approach using a series of Y-specific primers amplifying single DNA loci in Yq11. The order of all Y-DNA loci can be unequivocally arranged along the whole long Y arm. Therefore, any detected deletion can be quickly mapped in relation to the proposed position of AZF. Benefits and pitfalls of this new diagnostic Y screening method will be discussed.

p21(cip-1/waf-1) deficiency causes deformed nuclear architecture, centriole overduplication, polyploidy, and relaxed microtubule damage checkpoints in human hematopoietic cells.

A recent hypothesis suggests that tumor-specific killing by radiation and chemotherapy agents is due to defects or loss of cell cycle checkpoints. An important component of some checkpoints is p53-dependent induction of p21(cip-1/waf-1). Both p53 and p21 have been shown to be required for microtubule damage checkpoints in mitosis and in G1 phase of the cell cycle and they thus help to maintain genetic stability. We present here evidence that p21(cip-1/waf-1) deficiency relaxes the G1 phase microtubule checkpoint that is activated by microtubule damage induced with nocodazole. Reduced p21(cip-1/waf-1) expression also results in gross nuclear abnormalities and centriole overduplication. p53 has already been implicated in centrosome regulation. Our findings further suggest that the p53/p21 axis is involved in a checkpoint pathway that links the centriole/centrosome cycle and microtubule organization to the DNA replication cycle and thus helps to maintain genomic integrity. The inability to efficiently upregulate p21(cip-1/waf-1) in p21(cip-1/waf-1) antisense-expressing cells in response to microtubule damage could uncouple the centrosome cycle from the DNA cycle and lead to nuclear abnormalicies and polyploidy. A centrosome duplication checkpoint could be a new target for novel chemotherapy strategies.

Small marker chromosome identification in metaphase and interphase using centromeric multiplex fish (CM-FISH).

Multicolor karyotyping procedures, such as multiplex fluorescence in situ hybridization (M-FISH), spectral karyotyping, or color-changing karyotyping, can be used to detect chromosomal rearrangements and marker chromosomes in prenatal diagnosis, peripheral blood cultures, leukemia, and solid tumors, especially in cases where G-banding is not sufficient. A regular M-FISH analysis requires relatively large amounts of labeled DNA (microgram quantities), is not informative in interphase nuclei, hybridization can take up to 2 to 3 days, and unlabeled human chromosome-painting probes are not available commercially. Unique probes (plasmids, PAC), specific for centromeric or subtelomeric chromosomal regions, can replace the painting probes in M-FISH to address specific issues, such as the identification of marker chromosomes and aneuploidies. A set of plasmid probes carrying repetitive sequences specific for the alpha-satellite region of all human chromosomes were combined in a metaphase assay and an interphase assay, allowing identification of aneuploidies in one hybridization step, on a single cytogenetic slide. The fluorophore-dUTP and the labeled antibodies required to label and detect the DNA probes can be prepared in any laboratory. All DNA probes can be easily isolated and labeled using common molecular cytogenetic procedures. Because of the repetitive nature of the probes, hybridization time is short, usually less than 1 hour, and the analysis can be performed with nonspecialized image-processing software.

Improvements in cytogenetic slide preparation: controlled chromosome spreading, chemical aging and gradual denaturing.

BACKGROUND: Metaphase spreading is an essential technique for clinical and molecular cytogenetics. Results of classical banding techniques as well as complex fluorescent in situ hybridization (FISH) applications, such as comparative genomic hybridization (CGH) or multiplex FISH (M-FISH), are greatly influenced by the quality of chromosome spreading and pretreatment of the slide prior to hybridization. Materials and Methods Using hot steam and a metal plate with a temperature gradient across its surface, a reproducible protocol for slide preparation, aging, and hybridization was developed. RESULTS: This protocol yields good chromosome spreads from even the most difficult cell suspensions and is unaffected by the environmental conditions. Chromosome spreads were suitable for both banding and FISH techniques common to the cytogenetic laboratory. Chemical aging is a rapid slide pretreatment procedure for FISH applications, which allows freshly prepared cytogenetic slides to be used for in situ hybridization within 30 min, thus increasing analytical throughput and reducing benchwork. Furthermore, the gradually denaturing process described allows the use of fresh biologic material with optimal FISH results while protecting chromosomal integrity during denaturing. CONCLUSION: The slide preparation and slide pretreatment protocols can be performed in any laboratory, do not require specialized equipment, and provide robust results.

The human A1 adenosine receptor: ligand binding properties, sites of somatic expression and chromosomal localization.

The A1 adenosine receptor (A1AR) exerts important biological effects in the mammalian biology. To provide insights into the role A1AR action in human physiology, we characterized the pharmacologic properties of the human A1AR, examined somatic sites of A1AR gene expression, and identified the chromosomal location of the human A1AR gene. Using stably transfected CHO cells, the ligand binding properties of human and rat A1ARs were directly compared. Saturation studies showed that the human and rat A1ARs had similar high affinity for the A1 agonist [(3)H]CCPA (human, K(d)=517±64 pM; B(max) 438±29 fmol/mg of protein; rat, K(d)=429±69 pM; B(max) 358±76 fmol/mg of protein). Competition studies performed using seven adenosine agonists and four adenosine antagonists also did not detect differences in the ligand binding properties among the rat and human A1ARs. Northern analysis of 16 human tissues revealed the presence of a single hybridizing transcript of 2.5 kb. Human A1AR receptor mRNA expression was greatest in brain and testis; lower levels of A1AR mRNA were present in heart, pancreas, kidney and spleen. Southern blotting and PCR analysis of human-rodent somatic cell hybrids showed that the A1AR gene is on human chromosome 1. Using fluorescence in situ hybridization, the human A1AR gene was further localized to the 1q32.1 region. These observations show that the human A1AR is a high affinity receptor that has ligand binding properties similar to the rat A1AR, human A1AR mRNA is heavily expressed in brain and testis, and the gene encoding the human A1AR is present on the long arm of chromosome 1.