Biomedical subjects

H Ramachandran

Publications and source records attributed to H Ramachandran.

4 recordsLinked to original sources

PubMed2026

CRISPR/Cpf1-mediated knockout of FLG in human induced pluripotent stem cells generates a model for studying epidermal barrier dysfunction.

Loss of filaggrin (FLG) function impairs skin barrier formation and contributes to common inflammatory skin diseases. In this study, we established a FLG knockout human induced pluripotent stem cell (iPSC) line based on KOLF2.1 J using CRISPR/Cas12a (Cpf1)-mediated genome editing. A guide RNA targeting exon 2 introduced a homozygous mutation, which was confirmed by sequencing. The edited cells maintained typical pluripotent stem cell morphology, expressed key undifferentiated markers, and retained the ability to differentiate into all three germ layers. Karyotype and copy number variation (CNV) analyses confirmed genomic stability and parental origin; the cells were free of mycoplasma. This cell line enables studies of FLG-associated skin biology and pathology.

Humans↗

PubMed1992

Alternative splicing of the Schistosoma mansoni gene encoding a homologue of epidermal growth factor receptor.

The complete coding DNA for a Schistosoma mansoni homologue of the epidermal growth factor receptor (SER) was characterized from cDNA clones obtained by homology to the tyrosine kinase domain of erbB. The DNA sequence predicts a 200-kDa translation product that contains a secretory leader, a cysteine-rich extracellular domain, a hydrophobic transmembrane sequence, and an intracellular tyrosine kinase domain. The SER transcript is present in cercariae and adult schistosomes. In addition to SER transcripts, schistosomes produce at least 3 variant transcripts encoding truncated SER products that include the secretory leader and a small portion of the extracellular domain followed by short sequences of unrelated, C-terminal amino acids. Based on these sequences, 2 of the variant mRNAs (class 2 and 5) appear to encode soluble, secreted proteins while one (class 4) encodes an SER variant protein with a hydrophobic C-terminus that may serve as a membrane anchor. Class 2 SER variant transcripts are present at levels comparable to SER transcripts in adult worms but are not detected in cercariae. Class 4 and 5 SER variant transcripts are also found within adult worms but at lower levels. Genomic cloning and characterization demonstrate that the variant SER transcripts arise through alternative splicing of the SER gene.

Amino Acid Sequence↗

PubMed1988

Substitution of murine for human CD4 residues identifies amino acids critical for HIV-gp120 binding.

Human CD4 is the receptor for the gp120 envelope glycoprotein of human immunodeficiency virus and is essential for virus entry into the host cell. Sequence analysis of CD4 has suggested an evolutionary origin from a structure with four immunoglobulin-related domains. Only the two NH2-terminal domains are required to mediate gp120 binding. The extracellular segment of murine CD4 has an overall 50% identity with its human counterpart at the amino-acid level, but fails to bind gp120. To define those residues of human CD4 critical for gp120 binding, we have taken advantage of this species difference and substituted all non-conserved murine for human CD4 residues between amino-acid positions 27-167. We used oligonucleotide-directed mutagenesis to create each of 16 individual mutant human CD4 molecules containing from 1-4 amino-acid substitutions. Introduction of as few as three amino acids into corresponding positions of human CD4 abrogates gp120 binding. Furthermore, these critical residues are located in domain I with a contribution from domain II. Modelling studies using the three-dimensional coordinates of the V kappa Bence-Jones REI homodimer localize the site in domain I to the C" beta strand within CDR2 but projecting away from the homologues of principle antigen-binding regions CDR 1 and 3.

Amino Acid Sequence↗

PubMed1988

The gene for T11 (CD2) maps to chromosome 1 in humans and to chromosome 3 in mice.

The chromosomal locations of the human and murine T11 (CD2) gene have been determined. Using recently cloned cDNA to probe Southern blots of mouse X human and Chinese hamster X mouse somatic cell hybrids, we have localized the human T11 gene to chromosome 1 and the murine T11 gene to chromosome 3. Based on previously determined blocks of homology between human chromosome 1 and mouse chromosome 3, it is suggested that the human T11 gene may lie on the short arm of chromosome 1 proximal to p221. Thus, the T11 gene is not linked to any other genes for T cell markers that have been mapped to date.

Animals↗