# GENETIC STUDIES OF HUMAN SOMATIC CELLS

> **NIH NIH R01** · JOHNS HOPKINS UNIVERSITY · 1994 · $443,455

## Abstract

We plan to continue our investigations of X inactivation and
genomic imprinting in human females by exploring the molecular mechanisms.
As X inactivation is the means of X dosage compensation in all mammals and
features that differ among mammals are useful in dissecting components of
the mechanisms involved, we will continue studies of X inactivation in
marsupial and mouse as well as human cells.

     1.   Our previous studies of X inactivation in germ cells suggest that
gametic differences in DNA. methylation could provide the *molecular basis
for at least some phenomena attributed to parental differences in genomic
imprinting.  We will extend these studies by examining the methylation
status of pre-meiotic and meiotically arrested female germ cells, and
primordial germ cells of both sexes.  We will analyze methylation using
antibodies to 5-methylcytosine in histological preparations of gonads, and
develop a method for PCR amplification from small numbers of germ cells,
so as to examine specific HpaII sites.  Using in situ hybridization we will
determine if methyltransferase is expressed in unmethylated cells.

     2.   Our studies of marsupial cells show inactivity of the paternal
G6PD allele despite absence of DNA methylation and raise the possibility
that an inhibitor complex may be silencing the G6PD

locus.  We will look for such proteins using in vivo footprinting of the
G6PD-CpG island by, ligationmediated PCR.

     3. We will explore in more detail the role of DNA replication in
     reactivation and reversal of X
inactivation by examining replication of inactive and reactivated genes on
X chromosomes in mousehuman hybrid cells.

     4.   In search of sequences involved in early steps of X inactivation,
we will identify the X chromosome segment required for inactivation using
mouse-human hybrid cells containing X chromosomes with deletions in the
region considered to be the putative X inactivation center in mouse and
man.  To identify the "essential" segment we will define the minimal area
of overlapping sequences present on deleted human X chromosomes that are
inactive, and the limits for the region of homology with the putative
inactivation center on the mouse X, and will look for conserved cDNAs,
expressed in early mouse embryos and mapping to this segment.

## Key facts

- **NIH application ID:** 2194891
- **Project number:** 5R01HD005465-24
- **Recipient organization:** JOHNS HOPKINS UNIVERSITY
- **SAM.gov UEI:** FTMTDMBR29C7
- **Principal Investigator:** BARBARA R MIGEON
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1994
- **Award amount:** $443,455
- **Award type:** 5
- **Project period:** 1976-03-01 → 1996-02-29

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/2194891

## Citation

> US National Institutes of Health, RePORTER application 2194891, GENETIC STUDIES OF HUMAN SOMATIC CELLS (5R01HD005465-24). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/2194891. Licensed CC0.

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