Characterization of amino acids Arg, Ser and Thr at position 70 within HIV-1 reverse transcriptase

OBJECTIVES

The amino acid position 70 in HIV-1 reverse transcriptase (RT) plays an important role in nucleoside RT inhibitor (NRTI) resistance. K70R is part of the thymidine analog mutations, but also other amino acid changes have been associated with NRTI resistance, such as K70E and K70G. In this study, we investigated the in vivo selection of the HIV-1 RT mutations K70S and K70T and their in vitro effect on drug resistance and replication capacity.

METHODS

Recombinant viruses with RT mutations were generated to measure the in vitro drug susceptibility and replication capacity. Bayesian network analysis and three-dimensional modeling were performed to understand the selection and impact of the RT70 mutations.

RESULTS

K70S and K70T were found at a low frequency in RTI-experienced HIV-1 patients (0.10% and 0·20%). Baeyesian network learning identified no direct association with the in vivo exposure to any specific RTI. However, direct associations of K70S with mutations within the Q151M-complex and of K70T with K65R were observed. In vitro phenotypic testing revealed only minor effects of K70R/S/T as single mutations, associated with Q151M and within the context of the Q151M-complex.

DISCUSSION

These results suggest that the selection of K70S/T and their phenotypic impact are influenced by the presence of other mutations in RT. However, the low impact on in vitro phenotype here observed, alongside with the low in vivo prevalence, the exclusive direct association with known major RTI mutations and the unknown correlation with in vivo response, do not yet necessitate the inclusion of K70S/T in drug resistance interpretation systems.

Ectomorphic habitus, severe mental retardation and characteristic face: a new MCA/MR syndrome?

Here we report on 2 mentally retarded sisters with clinical signs and symptoms not seen in a previously delineated MCA/MR syndrome, i.e., normal pre- and perinatal history, severe mental retardation with severe delay in psychomotor development and without development of primary motor abilities and speech, characteristic face with maxillary hypoplasia, large mouth with down-turned corners, short philtrum and everted lower lip, associated with a remarkable ectomorphic habitus.

Profound mental retardation, characteristic facies with midfacial hypoplasia and premature frontotemporal balding, muscular hypotrophy, and small patellae in two unrelated male patients

Two profoundly mentally retarded, unrelated males are reported with an unidentified multiple congenital anomaly/mental retardation syndrome, including early balding, patella luxations, small hands and feet, and hypogonadism, similar to a previous publication in this journal of a severely mentally retarded male patient with dysmorphic features.

Effect of balanced X/autosome translocations on sexual and physical development. A personal experience in 4 patients

Four different balanced X/autosome translocations: 46,X,t(X;9)(p11;q13); 46,X,t(X;12) (p11;q12); 46,X,t(X;15)(q12;p11) and 46,X,t(X;19)(q26;p12) are described in four female patients. The effect of X/autosome translocations on physical and sexual development of these women and their offspring is discussed.

The Coffin-Lowry syndrome. A study of two new index patients and their families

Two adult, mentally retarded males with the typical features of the Coffin-Lowry syndrome are reported. Further family investigation led to the same diagnosis in a 2.5-year-old male cousin, and to the identification of five female carriers, with variable clinical expression of this X-linked inherited mental retardation syndrome.

Partial trisomy 18q12, due to intrachromosomal duplication, is not associated with typical 18 trisomy phenotype

Partial 18q12 trisomy, due to intrachromosomal duplication, was found in a severely mentally retarded boy. The finding of nonspecific dysmorphism in this patient demonstrates that trisomy of band 18q12 is accompanied by neither a full nor an incomplete 18 trisomy phenotype, indicating that this phenotype may be due solely to trisomy of the 18q11 band.

The Aarskog syndrome

In this report a description is given of the Aarskog syndrome in six males belonging to three different families. Partial expression of the syndrome was confirmed in two of the three examined obligate female heterozygotes, who had short stature, small hands and feet, short neck, and a round face with widow's peak and, in one of them, ptosis of the eyelids.

The Coffin syndrome

Two brothers with Coffin syndrome are presented and the fifteen other cases availabe in the literature are reviewed. The molecular defect causing this clinically recognizable syndrome is unknown, and the mode of inheritance may be a sex-linked recessive, but a sex-limited autosomal dominant or autosomal dominant with variable degree of expression cannot be fully excluded at the present time.