Converging evidence implicates the dopamine D3 receptor gene in vulnerability to schizophrenia

The dopamine D3 receptor has been implicated in the pathophysiology of schizophrenia (SZ). A glycine‐to‐serine polymorphism at codon 9 of the dopamine D3 receptor gene (DRD3), rs6280, has been widely studied for its association with SZ, but with conflicting results. Altered levels of DRD3 mRNA have also been reported in SZ compared with normal controls. Moreover, it has been suggested that DRD3 is subject to recent positive selection in European populations. To explore the potential role of DRD3 in SZ from these various aspects, we conducted a threefold study. First, we tested the genetic association of rs6280 with SZ in 685 SZ patients and 768 normal controls. Second, we examined DRD3 mRNA levels in peripheral leukocytes in a subset of 37 patients and 37 controls. Finally, we investigated the possible recent positive selection on DRD3 in an East Asian population. Consequently, we observed that the genotypic distribution of rs6280 was nominally associated with SZ (P = 0.045), with the ancestral CC genotype being significantly over‐represented in SZ patients. DRD3 mRNA levels were significantly lower in patients than in controls (P = 5.91E?5). The derived C‐allele of rs6280 might have been subject to recent positive selection (P < 0.001) in the East Asian population. Taken together, our results suggest that DRD3, a gene possibly under natural selection, might be involved in vulnerability to SZ in the Han Chinese population. These findings may further add to the body of data implicating DRD3 as a schizophrenia risk gene. © 2011 Wiley‐Liss, Inc.     

Conditional deletion of the Lkb1 gene in the mouse mammary gland induces tumour formation

Heterozygous germline mutations in the LKB1 (STK11) gene cause Peutz‐Jeghers syndrome (PJS), an autosomal dominant disorder characterized by hamartomatous polyposis of the gastrointestinal tract and an increased risk of colorectal, breast, and other cancers. To model the role of LKB1 mutation in mammary tumourigenesis, we have used a conditional gene targeting strategy to generate a mouse in which exons encoding the kinase domain of Lkb1 were deleted specifically in the mammary gland. Mammary gland tumours developed in these mice with a latency of 46–85 weeks and occurred in the thoracic or inguinal glands. These tumours were grade 2 invasive ductal carcinomas or solid papillary carcinomas with histological features similar to those described in breast cancers arising in patients with PJS. This mouse model of Lkb1 deficiency provides a potentially useful tool to investigate the role of Lkb1 in tumourigenesis and to guide the development of therapeutic approaches. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Vascular tumors of the mammary gland

Summary A total of five haemangiosarcomata and two benign haemangiomas arising in the mammary gland have been studied electron microscopically and by histochemical techniques. Malignant tumors were mainly composed of endothelial cells reactive to alkaline phosphatase and adenosine triphosphatase, and of pericytes and undifferentiated mesenchymal elements. A juvenile haemangioma showed a more structured wall with an increase of endoplasmic reticulum and filaments, and a diminution of membrane modulations and rod-like tubular bodies. A cavernous haemangioma showed an ultrastructure very similar to normal vessels.The ultrastructural and histochemical data suggest a blood vessel origin of mammary angiosarcomas and show that vascular neoplasms of the breast, benign or malignant, are composed of a combined proliferation of the different cell types present in the vessel wall, as described in other organs.Juvenile haemangioma and cavernous haemangioma show a more complex structure in their walls with stratification of the different types of cells and a continuous wall. The features of endothelium in juvenile haemangioma suggest a low functional activity rather than morphological de-differentiation.     

Involution of the sheep mammary gland

Changes in the ovine mammary gland epithelium during initiated involution were studied by light and electron microscopy. Apoptosis of the duct and alveolar epithelial cells was first identified at 2 d after weaning, reached a peak at 4 d and then progressed gradually thereafter. Apoptotic cells were phagocytosed by intraepithelial macrophages and alveolar epithelial cells. Occasional apoptotic epithelial cells were observed in the alveolar and duct lumina. The highly vacuolated cells in the alveolar and duct lumina were confirmed to be macrophages as they were CD45⁺, MHC class II⁺. Changes in myoepithelial cells involved shrinkage and extension of cytoplasmic processes into the underlying stroma and no apoptosis was observed. Regression of the blood capillaries was also by apoptosis. The resulting apoptotic bodies were either taken up by adjacent endothelial cells or were shed into the capillary lumen to be phagocytosed later by mural endothelial cells or blood monocytes. The mammary glands were completely involuted by 30 d after weaning. It was concluded that the mammary gland involutes by apoptosis, a process which allows deletion of cells without the loss of the basic architecture and the integrity of the epithelial lining of the gland.     

Identification and function of neonatal Fc receptor in mammary gland of lactating mice.

In addition to its proposed function in regulating serum IgG levels, the MHC class I-related neonatal Fc receptor (FcRn) is known to play a role in IgG transfer across rodent yolk sac and neonatal intestine. In contrast to humans, for which transplacental transfer of IgG appears to be the only mechanism of maternal IgG delivery, the transmission of IgG in mice occurs both antenatally (yolk sac) and neonatally (transport from mother's milk across intestinal epithelial cells). In the current study, a possible role for FcRn in regulating IgG transfer into milk has been investigated. FcRn has been shown to be present in functional form in the mammary gland of lactating mice, and is localized to the epithelial cells of the acini. Analysis of the transfer of Fc fragments and IgG which have different affinities for FcRn indicate that, unexpectedly, these proteins are transferred in inverse correlation with their binding affinity for FcRn. Thus, in the lactating mammary gland FcRn appears to play a role in recycling IgG in a mode that may have relevance to FcRn trafficking during the maintenance of constant serum IgG levels.     

Malignant oncocytoma of the mammary gland

Described in this paper is the morphological pattern of a malignant oncocytoma in the breast of a woman aged 70 years. The tumour parenchyma consisted mainly of epithelial cells grouped in nests or cords and surrounded by sparse fibrous stroma. The cells were quite large and pleomorphic, their nuclei being round or bizarre with prominent nucleoli. Electron microscopy revealed a conspicuously increased number of mitochondria and bundles of intracytoplasmic microfilaments.     

EMT tumorigenesis in the mouse mammary gland

The term EMT (epithelial-mesenchymal transition) is used in many settings. This term is used to describe the mechanisms facilitating cellular repositioning and redeployment during embryonic development and tissue reconstruction after injury. Recently, EMT has also been applied to potential mechanisms for malignant progression and has appeared as a specific diagnostic category of tumors. In mice, most 'EMT' tumors have a spindle cell phenotype. The definition of EMT is controversial because spindle cell tumors are not common in humans, especially in human breast cancers. Spindle cell tumors of the mouse mammary gland have been observed for many years where they are usually classified as sarcomas or carcinosarcomas. Genetically engineered mice develop mammary spindle cell tumors that appear to arise in the epithelium and undergo EMT. To better understand the origin and evolution of these spindle cell tumors in progression and metastases, seven cohorts of spindle cell tumors from the archives of the University of California, Davis Mutant Mouse Pathology Laboratory were studied. This study provides experimental and immunohistochemical evidence of EMT showing that dual epithelial and mesenchymal staining of tumor spindle cells identifies some, but not all, EMT-type tumors in the mouse. This suggests that potential EMT tumors are best designated EMT-phenotype tumors.     

Circadian clock and cell cycle gene expression in mouse mammary epithelial cells and in the developing mouse mammary gland.

Mouse mammary epithelial cells (HC-11) and mammary tissues were analyzed for developmental changes in circadian clock, cellular proliferation, and differentiation marker genes. Expression of the clock genes Per1 and Bmal1 were elevated in differentiated HC-11 cells, whereas Per2 mRNA levels were higher in undifferentiated cells. This differentiation-dependent profile of clock gene expression was consistent with that observed in mouse mammary glands, as Per1 and Bmal1 mRNA levels were elevated in late pregnant and lactating mammary tissues, whereas Per2 expression was higher in proliferating virgin and early pregnant glands. In both HC-11 cells and mammary glands, elevated Per2 expression was positively correlated with c-Myc and Cyclin D1 mRNA levels, whereas Per1 and Bmal1 expression changed in conjunction with beta-casein mRNA levels. Interestingly, developmental stage had differential effects on rhythms of clock gene expression in the mammary gland. These data suggest that circadian clock genes may play a role in mouse mammary gland development and differentiation.     

Gene expression in fibroadenomas of the rat mammary gland in contrast to spontaneous adenocarcinomas and normal mammary gland.

Fibroadenomas are considered a benign lesion in rodent carcinogenicity studies. However, the entity adenocarcinoma arising in fibroadenoma does exist and in humans there is evidence of certain forms of fibroadenomas to confer greater risk of subsequent breast cancer. In this study, we aim to elucidate the molecular features of both spontaneous fibroadenomas and adenocarcinomas. The gene expression of the two tumour types is examined and compared to mammary gland in the same developmental state and examined for similarities which might indicate common molecular pathways. In the present study no similarities were discovered. We conclude that in the tumours examined here, no progression to adenocarcinoma is likely. Further studies are needed, examining a greater number of tumours and including cases of adenocarcinoma arising in fibroadenoma.     

Secretory phenomena in the non-lactating human mammary gland

The normal non-lactating premenopausal human mammary gland has been shown by immunohistochemistry and transmission electron microscopy to secrete a number of antimicrobial peptides such as beta-defensins, the cathelicidin LL37, lactoferrin and adrenomedullin. In addition, the non-lactating gland elaborates a prominent glycocalyx at the apical membrane of the glandular epithelial cells, parts of which are shed into the lumen of endpieces and ducts. This glycocalyx includes the mucins MUC 1 and MUC 4, a strongly Alcian Blue positive palyanionic component and sulfated material stained with Aldehyde Fuchsin. MUC 1 and the Alcian Blue positive material are considered to play an antimicrobial role, too. Lactalbumin and lipid droplets also occur in the non-lactating gland. At the EM-level secretory phenomena operating by exocytosis and by means of the apocrine mechanism have been observed. Cytoskeletal components presumably play a role in apocrine secretion. Apart from secretion at the cellular apex, secretion at the cellular basis also occurs regularly, which may represent the production of para- or endocrine factors.     

Site of lodination in rat mammary gland

The ability of the mammary gland to take up and organically bind radioiodide was studied in non-pregnant, pregnant, and lactating rats. Autoradiography was used to determine whether duct cells or alveolar cells are responsible for iodination in the rat mammary gland. Iodination was not detected in mammary glands from non-pregnant rats, but occurred late in the twelfth day of gestation and continued throughout pregnancy and lactation. Protein-containing vacuoles in alveolar cells and casein-like proteins in milk were the major sites where iodination occurred within the gland. Milk proteins in the lumens of ductules adjacent to alveoli were also iodinated. In contrast, ducts, myoepithelial cells, fat cells, blood vessels and other histological components of the gland did not show iodinating capability. Cytochemistry was also used to identify endogenous mammary peroxidase activity in the same glands, and it was found that the presence and location of this enzyme was correlated with the ability to iodinate.     

Histamine in C3H/W mice carrying spontaneous tumors of the mammary gland

Adenocarcinoma mammae, a spontaneously growing mammary cancer in C3H/W mice, contrary to many transplanted tumors does not evoke any rise in histamine level either in the tumor or in distant tissues. On the other hand, the histamine level is reduced by 90% in the tumor in comparison with the healthy gland. This seems to be a consequence of the fall of histidine decarboxylase activity to below a detectable level. There is also a significant reduction in histamine N-methyltransferase activity to onefifth of the control level. The healthy mammary gland contains a high concentration of histamine and catabolizes it exclusively through the methylation pathway.     

Immune-mediated inflammation in the lumen of the bovine mammary gland

Two groups of cows were sensitized to ovalbumin (OA) during lactation by a subcutaneous injection of OA either in Freund's complete or incomplet adjuvant; two groups of animals injected with the respective adjuvants only served as controls. Intraluminal infusion of microgram quantities of OA in uninflamed mammary glands elicited inflammation, i.e., release of leukocytes into the milk, only in the animals previously sensitized to OA. This indicates that an antigen-specific inflammatory pathway can be established in the mammary gland by parenteral sensitization. Immune-mediated release of leukocytes into the milk could not be reproduced by infusing complement fixing. OA-anti-OA complexes into the lumen of uninflamed glands of unsensitized cows.