Marsha M. Goldstein

Identification and localization of TBX5 transcription factor during human cardiac morphogenesis

Mutations in the TBX5 transcription factor gene cause human cardiac malformation in Holt‐Oram syndrome. To identify and localize TBX5 during cardiac morphogenesis, we performed immunohistochemical studies of TBX5 protein cardiac expression during human embryogenesis. Specific antibody to human TBX5 was generated in rabbits with a TBX5 synthetic peptide and affinity purification of antiserum. Anti‐TBX5 was used in immunohistochemical analyses of human cardiac tissue. In embryonic and adult heart, TBX5 is expressed throughout the epicardium and in cardiomyocyte nuclei in myocardium of all four cardiac chambers. Endocardial expression of TBX5 is only present in left ventricle. Asymmetric left‐sided transmyocardial gradients of TBX5 protein expression were observed in embryonic but not adult hearts. Human cardiac expression of TBX5 protein correlates with the cardiac manifestations of Holt‐Oram syndrome. TBX5 transmyocardial protein gradients may contribute to normal patterning of the human heart during embryogenesis.

Molecular genetic diagnosis of the familial myxoma syndrome (Carney complex)

We describe an individual in whom molecular genetic testing provided a diagnosis of the Carney complex, an autosomal dominant syndrome comprising cutaneous and cardiac myxomas, spotty pigmentation of the skin, and endocrinopathy. Recently, we localized the Carney complex disease gene to chromosome region 17q2. Our patient was a member of a family segregating the Carney complex, but was not, himself, initially thought to be affected. Haplotype analysis based on genotyping studies with 17q2 microsatellites predicted that this individual was, in fact, affected by Carney complex and was at risk for development of myxomas. Further clinical evaluation and re-review of prior pathologic studies, then, confirmed the DNA-based diagnosis. This report highlights the difficulty in establishing a diagnosis of Carney complex based on clinical and pathologic findings alone, and we suggest that molecular genetic analyses provide an important diagnostic method for this familial myxoma syndrome.

Mice transgenic for monocyte-tropic HIV type 1 produce infectious virus and display plasma viremia: a new in vivo system for studying the postintegration phase of HIV replication.

To generate an in vivo system for investigating the postintegration phase of HIV-1 replication, mouse lines transgenic for a full-length infectious proviral clone of a monocyte-tropic HIV-1 isolate, HIV-1JR-CSF, were constructed. Leukocytes from two independent JR-CSF transgenic mouse lines produced HIV-1 that infected human PBMCs. Plasma viremia was detected in these mice at levels (mean, >60,000 HIV RNA copies/ml) comparable to those reported for HIV-1-infected individuals. The levels of HIV RNA in these mice increased several-fold after either treatment with the superantigen Staphylococcus enterotoxin B or infection with Mycobacterium tuberculosis. Thus, a provirus encoding a monocyte-tropic HIV-1 strain under the control of its LTR expressed as a transgene in mice can proceed through the postintegration replication phase and produce infectious virus. In addition, the presence of plasma viremia that can be monitored by measuring plasma HIV-1 RNA levels permits these mice to be used to study the impact of different interventions on modulating in vivo HIV-1 production. Therefore, these mice provide a novel manipulable system to investigate the in vivo regulation of HIV-1 production by factors that activate the immune system. Furthermore, this murine system should be useful in delineating the role of human-specific factors in modulating HIV-1 replication and investigating the in vivo therapeutic efficacy of agents that target the postintegration stages of HIV-1 replication.