Clinicocytopathological spectrum, including uncommon forms, of nine cases of chordomas with immunohistochemical results, including brachyury immunostaining: A single institutional experience.

OBJECTIVES: To present clinical and cytopathological features of nine cases of chordomas, diagnosed over 9 years and confirmed by brachyury (T) immunostaining. METHODS: Conventional cytological smears, stained with Papanicolaou and May-Grünwald Giemsa, along with corresponding histopathological (n = 8) and immunostained sections (n = 8) were reviewed. Immunohistochemical staining was performed on tissue sections by polymer detection technique. RESULTS: Nine tumours occurred in seven males and two females, with age ranging from 36 to 72 years (average = 58.7), in the sacrum (seven) and spine (two). On fine needle aspiration cytology, five cases were either diagnosed with or diagnosed with a suggestion of a chordoma, while three cases were diagnosed with chordoma as a differential diagnosis. On review, smears were moderately cellular, comprising myxoid stroma (9/9), epithelioid cells (9/9), physaliphorous cells (8/9), including binucleation (7/9), prominent nucleolisation (2/9), pleomorphic cells (2/9) and intranuclear inclusions (3/9). Immunohistochemically, tumour cells expressed cytokeratin (4/4), pan cytokeratin (4/4), epithelial membrane antigen (8/8), S100 protein (6/8) and brachyury (8/8). Five patients underwent surgical excision, including two who underwent adjuvant radiotherapy (RT) and four patients who underwent RT. During follow-up (n = 8), a single patient developed recurrence and another presented with metastatic lesions. Finally, five patients were alive with disease (7-53 months); a single patient was free of disease (4 months), and two patients died of disease; the latter cases displayed pleomorphic cells and intranuclear inclusions. CONCLUSIONS: Chordomas can be primarily diagnosed by fine needle aspiration cytology in a typical clinicoradiological setting with a combination of key cytomorphological features. Pleomorphic cells and intranuclear inclusions are associated with a relatively aggressive subtype. An exact diagnosis has treatment implications and requires confirmation by brachyury immunostaining.

Expression of tbx20 RNA during chick heart development.

The T-box gene family encodes a set of transcription factors that are involved in various developmental processes. We isolated tbx20 gene from chick embryos and examined in detail its expression patterns during heart development. In situ hybridization showed that tbx20 was expressed in the lateral plate mesoderm and subsequently in the primitive heart tube. At stages of looped heart, tbx20 was localized in the outflow tract (OT) and atrioventricular (AV) canal, in which valvuloseptal endocardial cushion develops. At later stages, although tbx20 was expressed predominantly in the nascent right ventricle, transcripts of tbx20 were down-regulated in the left ventricle. These results suggest that tbx20 may play important roles in a variety of developmental processes in cardiogenesis, such as chamber-specification and septation.

Vax2 inactivation in mouse determines alteration of the eye dorsal-ventral axis, misrouting of the optic fibres and eye coloboma.

Vax2 is a homeobox gene whose expression is confined to the ventral region of the prospective neural retina. Overexpression of this gene at early stages of development in Xenopus and in chicken embryos determines a ventralisation of the retina, thus suggesting its role in the molecular pathway that underlies eye development. We describe the generation and characterisation of a mouse with a targeted null mutation of the Vax2 gene. Vax2 homozygous mutant mice display incomplete closure of the optic fissure that leads to eye coloboma. This phenotype is not fully penetrant, suggesting that additional factors contribute to its generation. Vax2 inactivation determines dorsalisation of the expression of mid-late (Ephb2 and Efnb2) but not early (Pax2 and Tbx5) markers of dorsal-ventral polarity in the developing retina. Finally, Vax2 mutant mice exhibit abnormal projections of ventral retinal ganglion cells. In particular, we observed the almost complete absence of ipsilaterally projecting retinal ganglion cells axons in the optic chiasm and alteration of the retinocollicular projections. All these findings indicate that Vax2 is required for the proper closure of the optic fissure, for the establishment of a physiological asymmetry on the dorsal-ventral axis of the eye and for the formation of appropriate retinocollicular connections.

Senescence bypass screen identifies TBX2, which represses Cdkn2a (p19(ARF)) and is amplified in a subset of human breast cancers.

To identify new immortalizing genes with potential roles in tumorigenesis, we performed a genetic screen aimed to bypass the rapid and tight senescence arrest of primary fibroblasts deficient for the oncogene Bmi1. We identified the T-box member TBX2 as a potent immortalizing gene that acts by downregulating Cdkn2a (p19(ARF)). TBX2 represses the Cdkn2a (p19(ARF)) promoter and attenuates E2F1, Myc or HRAS-mediated induction of Cdkn2a (p19(ARF)). We found TBX2 to be amplified in a subset of primary human breast cancers, indicating that it might contribute to breast cancer development.

A vegetally localized T-box transcription factor in Xenopus eggs specifies mesoderm and endoderm and is essential for embryonic mesoderm formation.

Pattern formation in early embryogenesis is guided by maternal, localized determinants and by inductive interactions between cells. In Xenopus eggs, localized molecules have been identified and some, such as Vg1 and Xwnt-11, can specify cell fates by functioning as inducers or patterning agents. We have used differential screening to identify new Xenopus genes that regulate mesodermal patterning, and we have isolated a new member of the T-box family of transcription factors. This gene, named Brat, is expressed maternally and its transcripts are localized to the vegetal hemisphere of the egg. During early embryonic cleavage, Brat mRNA becomes partitioned primarily within vegetal cells that are fated to form the endoderm. Zygotic expression of Brat begins at the onset of gastrulation within the presumptive mesoderm of the marginal zone. Consistent with its zygotic expression pattern, Brat induces, in a dose-dependent manner, a full spectrum of mesodermal genes that mark tissues across the dorsal-ventral axis, from the blood through the Spemann organizer. Brat also induces endoderm, consistent with its vegetal localization, making Brat a good candidate for a maternal determinant of the endoderm. We tested whether endogenous Brat is required for mesoderm formation by expressing a dominant-negative, transcriptional repressor form of Brat in embryos. This treatment inhibited mesoderm formation and severely disrupted normal development, thereby establishing that Brat plays a critical role in embryonic mesoderm formation and body patterning.